blocks|key|2052359|text|在过滤过程中，我可能会使用一个标志对象(编辑:我不会再使用了，请看答案末尾关于use+2015的Set__的注释)，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2052360|var+flags+=+{};
var+newPlaces+=+places.filter(function(entry)+{
++++if+(flags[entry.city])+{
++++++++return+false;
++++}
++++flags[entry.city]+=+true;
++++return+true;
});|code-block|syntax|javascript|2052361|它使用Array#filter+(来自ECMAScript5+(+ES5+)+)，这是可以抖动的ES5添加内容之一(搜索几个选项的"es5+shim“)。|2052362|您可以不使用filter来完成它，当然，它只是有点冗长：|2052363|var+flags+=+{};
var+newPlaces+=+[];
var+index;
for+(index+=+0;+index+<+places.length;+%2B%2Bindex)+{
++++if+(!flags[entry.city])+{
++++++++flags[entry.city]+=+true;
++++++++newPlaces.push(entry);
++++}
});|2052364|上述两种假设都假设应该保留具有给定城市的第一个对象，而所有其他对象都应被丢弃。|2052365|注意:正如user2736012在下面指出的那样，我的测试if+(flags[entry.city])对于具有与Object.prototype上存在的属性(如toString+)相同的名称的城市来说是正确的。在这种情况下不太可能，但有四种方法可以避免这种可能性：|2052366|(我通常喜欢的解决方案)创建没有原型的对象：var+flags+=+Object.create(null);。这是ES5的一个特性。请注意，对于IE8这样的过时浏览器(+Object.create的单参数版本可以是null，除非该参数的值是null)，这是不可能的。|unordered-list-item|2052367|在测试中使用hasOwnProperty，例如if+(flags.hasOwnProperty(entry.city))|2052368|为任何Object.prototype属性(如xx)添加一个前缀，您知道该前缀不存在：
var+key+=+"xx“%2B+entry.city；if+(标记键){+//+.}标记键=+true；|2052369|在ES2015中，您可以使用Set来代替：
const标志=新集()；const+newPlaces+=places.filter(条目=>+{+if+(flags.has(entry.city){返回false；}+flags.add(entry.city)；返回true；}；|2052370|entityMap|0|LINK|mutability|MUTABLE|url|http://www.ecma-international.org/ecma-262/5.1/#sec-15.4.4.20^0|1C|3|0|0|3|C|3|C|0|0|6|6|0|0|0|T|M|1K|G|28|8|0|M|W|2D|D|2Z|4|3C|4|0|6|E|N|11|0|3|G|N|2|0|E|3|0^^$0|@$1|2|3|4|5|6|7|1B|8|@$9|1C|A|1D|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1E|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1F|8|@$9|1G|A|1H|B|C]]|D|@$9|1I|A|1J|1|1K]]|E|$]]|$1|M|3|N|5|6|7|1L|8|@$9|1M|A|1N|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|1O|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|1P|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1Q|8|@$9|1R|A|1S|B|C]|$9|1T|A|1U|B|C]|$9|1V|A|1W|B|C]]|D|@]|E|$]]|$1|U|3|V|5|W|7|1X|8|@$9|1Y|A|1Z|B|C]|$9|20|A|21|B|C]|$9|22|A|23|B|C]|$9|24|A|25|B|C]]|D|@]|E|$]]|$1|X|3|Y|5|W|7|26|8|@$9|27|A|28|B|C]|$9|29|A|2A|B|C]]|D|@]|E|$]]|$1|Z|3|10|5|W|7|2B|8|@$9|2C|A|2D|B|C]|$9|2E|A|2F|B|C]]|D|@]|E|$]]|$1|11|3|12|5|W|7|2G|8|@$9|2H|A|2I|B|C]]|D|@]|E|$]]|$1|13|3|-4|5|6|7|2J|8|@]|D|@]|E|$]]]|14|$15|$5|16|17|18|E|$19|1A]]]]

I'd probably use a flags object during the filtering (edit: I wouldn't anymore, see the note at the end of the answer about ES2015's <code>Set</code>), like this:
<pre><code>var flags = {};
var newPlaces = places.filter(function(entry) {
 if (flags[entry.city]) {
 return false;
 }
 flags[entry.city] = true;
 return true;
});
</code></pre>
That uses <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-15.4.4.20" rel="nofollow noreferrer"><code>Array#filter</code></a> from ECMAScript5 (ES5), which is one of the ES5 additions that can be shimmed (search for &quot;es5 shim&quot; for several options).
You can do it without <code>filter</code>, of course, it's just a bit more verbose:
<pre><code>var flags = {};
var newPlaces = [];
var index;
for (index = 0; index &lt; places.length; ++index) {
 if (!flags[entry.city]) {
 flags[entry.city] = true;
 newPlaces.push(entry);
 }
});
</code></pre>
Both of the above assume the first object with a given city should be kept, and all other discarded.
<hr />
Note: As user2736012 points out below, my test <code>if (flags[entry.city])</code> will be true for cities with names that happen to be the same as properties that exist on <code>Object.prototype</code> such as <code>toString</code>. Very unlikely in this case, but there are four ways to avoid the possibility:
<ul>
<li>(My usual preferred solution) Create the object without a prototype: <code>var flags = Object.create(null);</code>. This is a feature of ES5. Note that this cannot be shimmed for obsolete browsers like IE8 (the single-argument version of <code>Object.create</code> can be except when that argument's value is <code>null</code>).
</li>
<li>Use <code>hasOwnProperty</code> for the test, e.g. <code>if (flags.hasOwnProperty(entry.city))</code>
</li>
<li>Put a prefix on that you know doesn't exist for any <code>Object.prototype</code> property, such as <code>xx</code>:
<pre><code> var key = &quot;xx&quot; + entry.city;
 if (flags[key]) {
 // ...
 }
 flags[key] = true;
</code></pre>
</li>
<li>As of ES2015, you could use a <code>Set</code> instead:
<pre><code> const flags = new Set();
 const newPlaces = places.filter(entry =&gt; {
 if (flags.has(entry.city)) {
 return false;
 }
 flags.add(entry.city);
 return true;
 });
</code></pre>
</li>
</ul>

blocks|key|64246|text|正如注释中所指出的，您可以使用一个对象作为映射，这将允许您避免重复，然后您可以枚举对象的属性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|64247|工作小提琴：http://jsfiddle.net/gPRPQ/1/|offset|length|64248|var+places+=+[];
var+a+=+{};
a.lat+=+12.123;
a.lng+=+13.213;
a.city+=+"New+York";

places.push(a);

var+b+=+{};
b.lat+=+3.123;
b.lng+=+2.213;
b.city+=+"New+York";

places.push(b);

var+unique+=+{}

for+(var+i+=+0;+i+<+places.length;+i%2B%2B)+{
++++var+place+=+places[i];
++++unique[place.city]+=+place;
}

for+(var+name+in+unique)+{
++++var+place+=+unique[name];
++++console.log(place);
}|code-block|syntax|javascript|64249|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/gPRPQ/1/^0|0|6|S|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

As pointed out in the comments, you could use an object as a map, which will allow you to avoid duplicates, you can then enumerate the properties of the object.

working fiddle: <a href="http://jsfiddle.net/gPRPQ/1/" rel="nofollow">http://jsfiddle.net/gPRPQ/1/</a>

<pre><code>var places = [];
var a = {};
a.lat = 12.123;
a.lng = 13.213;
a.city = "New York";

places.push(a);

var b = {};
b.lat = 3.123;
b.lng = 2.213;
b.city = "New York";

places.push(b);

var unique = {}

for (var i = 0; i &lt; places.length; i++) {
 var place = places[i];
 unique[place.city] = place;
}

for (var name in unique) {
 var place = unique[name];
 console.log(place);
}
</code></pre>

blocks|key|975838|text|我的建议：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|975839|Array.prototype.uniqueCity+=+function()+{
++++var+processed+=+[];
++++for+(var+i=this.length-1;+i>=0;+i--){
++++++++if+(processed.indexOf(this[i].city)<0)+{
++++++++++++processed.push(this[i].city);
++++++++}+else+{
++++++++++++this.splice(i,+1);
++++++++}
++++}
}|code-block|syntax|javascript|975840|在使用中：|975841|places.uniqueCity();|975842|或|975843|Array.prototype.uniqueObjectArray+=+function(field)+{
++++var+processed+=+[];
++++for+(var+i=this.length-1;+i>=0;+i--)+{
++++++++if+(this[i].hasOwnProperty(field))+{
++++++++++++if+(processed.indexOf(this[i][field])<0)+{
++++++++++++++++processed.push(this[i][field]);
++++++++++++}+else+{
++++++++++++++++this.splice(i,+1);
++++++++++++}
++++++++}
++++}
}

places.uniqueObjectArray('city');|975844|使用上面的内容，您可以根据对象中的任何字段对数组进行排序，即使它们不存在于某些对象中。|975845|975846|function+uniqueCity(array)+{
++++var+processed+=+[];
++++for+(var+i=array.length-1;+i>=0;+i--){
++++++++if+(processed.indexOf(array[i].city)<0)+{
++++++++++++processed.push(array[i].city);
++++++++}+else+{
++++++++++++array.splice(i,+1);
++++++++}
++++}
++++return+array;
}

places+=+uniqueCity(places);|975847|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|X|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Z|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|11|8|@]|9|@]|A|$]]|$1|Q|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|R|3|S|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|T|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|U|$]]

My suggestion :

<pre><code>Array.prototype.uniqueCity = function() {
 var processed = [];
 for (var i=this.length-1; i&gt;=0; i--){
 if (processed.indexOf(this[i].city)&lt;0) {
 processed.push(this[i].city);
 } else {
 this.splice(i, 1);
 }
 }
}
</code></pre>

in use :

<pre><code>places.uniqueCity();
</code></pre>

or

<pre><code>Array.prototype.uniqueObjectArray = function(field) {
 var processed = [];
 for (var i=this.length-1; i&gt;=0; i--) {
 if (this[i].hasOwnProperty(field)) {
 if (processed.indexOf(this[i][field])&lt;0) {
 processed.push(this[i][field]);
 } else {
 this.splice(i, 1);
 }
 }
 }
}

places.uniqueObjectArray('city');
</code></pre>

With the above you can sort the array by any of the fields in the objects, even if they are not present for some of the objects.

or

<pre><code>function uniqueCity(array) {
 var processed = [];
 for (var i=array.length-1; i&gt;=0; i--){
 if (processed.indexOf(array[i].city)&lt;0) {
 processed.push(array[i].city);
 } else {
 array.splice(i, 1);
 }
 }
 return array;
}

places = uniqueCity(places);
</code></pre>

blocks|key|2052388|text|https://lodash.com/docs#uniqBy|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2052389|https://github.com/lodash/lodash/blob/4.13.1/lodash.js#L7711|2052390|/**
+*+This+method+is+like+`_.uniq`+except+that+it+accepts+`iteratee`+which+is
+*+invoked+for+each+element+in+`array`+to+generate+the+criterion+by+which
+*+uniqueness+is+computed.+The+iteratee+is+invoked+with+one+argument:+(value).
+*
+*+@static
+*+@memberOf+_
+*+@since+4.0.0
+*+@category+Array
+*+@param+{Array}+array+The+array+to+inspect.
+*+@param+{Array%7CFunction%7CObject%7Cstring}+[iteratee=_.identity]
+*++The+iteratee+invoked+per+element.
+*+@returns+{Array}+Returns+the+new+duplicate+free+array.
+*+@example
+*
+*+_.uniqBy([2.1,+1.2,+2.3],+Math.floor);
+*+//+=>+[2.1,+1.2]
+*
+*+//+The+`_.property`+iteratee+shorthand.
+*+_.uniqBy([{+'x':+1+},+{+'x':+2+},+{+'x':+1+}],+'x');
+*+//+=>+[{+'x':+1+},+{+'x':+2+}]
+*/|code-block|syntax|javascript|2052391|entityMap|0|LINK|mutability|MUTABLE|url|1^0|0|U|0|0|0|1O|1|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|F|3|G|5|H|7|10|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|4]]|R|$5|N|O|P|C|$Q|E]]]]

<a href="https://lodash.com/docs#uniqBy" rel="noreferrer">https://lodash.com/docs#uniqBy</a>

<a href="https://github.com/lodash/lodash/blob/4.13.1/lodash.js#L7711" rel="noreferrer">https://github.com/lodash/lodash/blob/4.13.1/lodash.js#L7711</a>

<pre><code>/**
 * This method is like `_.uniq` except that it accepts `iteratee` which is
 * invoked for each element in `array` to generate the criterion by which
 * uniqueness is computed. The iteratee is invoked with one argument: (value).
 *
 * @static
 * @memberOf _
 * @since 4.0.0
 * @category Array
 * @param {Array} array The array to inspect.
 * @param {Array|Function|Object|string} [iteratee=_.identity]
 * The iteratee invoked per element.
 * @returns {Array} Returns the new duplicate free array.
 * @example
 *
 * _.uniqBy([2.1, 1.2, 2.3], Math.floor);
 * // =&gt; [2.1, 1.2]
 *
 * // The `_.property` iteratee shorthand.
 * _.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
 * // =&gt; [{ 'x': 1 }, { 'x': 2 }]
 */
</code></pre>

blocks|key|975875|text|这条线可能很旧，但我认为我应该分享它。它基于纯JavaScript，并根据指定的属性删除重复的对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|975876|function+removeDuplicates(originalArray,+properties)+{
++var+newArray+=+[];
++var+index+=+0;
++var+lookupObject+=+{};
++var+totalProperties+=+properties.length;

++for+(var+i+=+0;+i+<+originalArray.length;+i%2B%2B)+{
++++var+exists+=+false;

++++for+(var+a+=+0;+a+<+newArray.length;+a%2B%2B)+{
++++++var+propsFound+=+0;
++++++for+(var+b+=+0;+b+<+totalProperties;+b%2B%2B)+{
++++++++if+(originalArray[i][properties[b]]+==+newArray[a][properties[b]])+{
++++++++++propsFound%2B%2B;
++++++++}
++++++}

++++++//If+there+is+a+match+then+break+the+for+loop
++++++if+(propsFound+==+totalProperties)+{
++++++++exists+=+true;
++++++++break;
++++++}
++++}+//End+of+New+Array

++++if+(!exists)+{
++++++newArray[index]+=+originalArray[i];
++++++index%2B%2B;
++++}
++}+//End+of+originalArray

++return+newArray;
}|code-block|syntax|javascript|975877|你可以看到小提琴这里|offset|length|975878|entityMap|0|LINK|mutability|MUTABLE|url|https://jsfiddle.net/programmerboy/wdv4ezyr/2/^0|0|0|8|2|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

This thread may be old but thought I should share it. It is based on Pure JavaScript and removes Duplicate Objects based on the Properties Specified.

<pre><code>function removeDuplicates(originalArray, properties) {
 var newArray = [];
 var index = 0;
 var lookupObject = {};
 var totalProperties = properties.length;

 for (var i = 0; i &lt; originalArray.length; i++) {
 var exists = false;

 for (var a = 0; a &lt; newArray.length; a++) {
 var propsFound = 0;
 for (var b = 0; b &lt; totalProperties; b++) {
 if (originalArray[i][properties[b]] == newArray[a][properties[b]]) {
 propsFound++;
 }
 }

 //If there is a match then break the for loop
 if (propsFound == totalProperties) {
 exists = true;
 break;
 }
 } //End of New Array

 if (!exists) {
 newArray[index] = originalArray[i];
 index++;
 }
 } //End of originalArray

 return newArray;
}
</code></pre>

You can view the fiddle <a href="https://jsfiddle.net/programmerboy/wdv4ezyr/2/" rel="nofollow noreferrer">here</a>

blocks|key|2052416|text|var+places+=+[];
var+a+=+{};
a.lat+=+12.123;
a.lng+=+13.213;
a.city+=+"New+York";

places.push(a);

var+b+=+{};
b.lat+=+3.123;
b.lng+=+2.213;
b.city+=+"New+York";

places.push(b);

getUniqAR(places,'city');+//Return+Uniq+Array+by+property

function+getUniqAR(Data,filter){
var+uniar+=[];
Data.forEach(function(item,ind,arr){
++++var+dupi=false;
++++if(!uniar.length)+uniar.push(item)+//push+first+obj+into+uniq+array+
++++uniar.forEach(function(item2,+ind2,arr){
++++if(item2[filter]+==+item[filter]){++//check+each+obj+prop+of+uniq+array+
++++++dupi=true;+//if+values+are+same+put+duplicate+is+true
++++++++}+++++
++++})
if(!dupi){++uniar.push(item)}+//if+no+duplicate+insert+to+uniq

})
console.log(uniar)
return+uniar;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2052417|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var places = [];
var a = {};
a.lat = 12.123;
a.lng = 13.213;
a.city = "New York";

places.push(a);

var b = {};
b.lat = 3.123;
b.lng = 2.213;
b.city = "New York";

places.push(b);

getUniqAR(places,'city'); //Return Uniq Array by property

function getUniqAR(Data,filter){
var uniar =[];
Data.forEach(function(item,ind,arr){
 var dupi=false;
 if(!uniar.length) uniar.push(item) //push first obj into uniq array 
 uniar.forEach(function(item2, ind2,arr){
 if(item2[filter] == item[filter]){ //check each obj prop of uniq array 
 dupi=true; //if values are same put duplicate is true
 } 
 })
if(!dupi){ uniar.push(item)} //if no duplicate insert to uniq

})
console.log(uniar)
return uniar;
}
</code></pre>

blocks|key|64288|text|我在@IgorL解决方案上做了一些扩展，但扩展了prototype，给它提供了一个选择器函数，而不是一个属性，以使它更加灵活：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|64289|Array.prototype.unique+=+function(selector)+{
+++return+this.filter((e,+i)+=>+this.findIndex((a)+=>+{
++++++if+(selector)+{
++++++++return+selector(a)+===+selector(e);
++++++}
++++++return+a+===+e;
++++})+===+i);
};|code-block|syntax|javascript|64290|使用：|offset|length|style|BOLD|64291|//+with+no+param+it+uses+strict+equals+(===)+against+the+object
let+primArr+=+['one','one','two','three','one']
primArr.unique()+//+['one','two','three']

let+a+=+{foo:123}
let+b+=+{foo:123}
let+fooArr+=+[a,a,b]
fooArr.unique()+//[a,b]

//+alternatively,+you+can+pass+a+selector+function
fooArr.unique(item=>item.foo)+//[{foo:123}]+(first+"unique"+item+returned)|64292|当然，这不是最具表现力的方法，但只要选择器是简单的，并且数组不是很大，它就应该工作得很好。|64293|打字本|64294|Array.prototype.unique+=+function<T>(this:+T[],+selector?:+(item:+T)+=>+object):+T[]+{
+++return+this.filter((e,+i)+=>+this.findIndex((a)+=>+{
++++++if+(selector)+{
++++++++return+selector(a)+===+selector(e);
++++++}
++++++return+a+===+e;
++++})+===+i);
};|64295|entityMap^0|0|0|0|3|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

I expanded a bit on @IgorL solution, but extended prototype and gave it a selector function instead of a property to make it a little more flexible:

<pre><code>Array.prototype.unique = function(selector) {
 return this.filter((e, i) =&gt; this.findIndex((a) =&gt; {
 if (selector) {
 return selector(a) === selector(e);
 }
 return a === e;
 }) === i);
};
</code></pre>

Usage:

<pre><code>// with no param it uses strict equals (===) against the object
let primArr = ['one','one','two','three','one']
primArr.unique() // ['one','two','three']

let a = {foo:123}
let b = {foo:123}
let fooArr = [a,a,b]
fooArr.unique() //[a,b]

// alternatively, you can pass a selector function
fooArr.unique(item=&gt;item.foo) //[{foo:123}] (first "unique" item returned)
</code></pre>

Definitely NOT the most performant way to do this but as long as the selector is simple and the array isn't massive, it should work fine.

<h2>In Typescript</h2>

<pre><code>Array.prototype.unique = function&lt;T&gt;(this: T[], selector?: (item: T) =&gt; object): T[] {
 return this.filter((e, i) =&gt; this.findIndex((a) =&gt; {
 if (selector) {
 return selector(a) === selector(e);
 }
 return a === e;
 }) === i);
};
</code></pre>

blocks|key|2052493|text|您可以使用Map，以便具有相同键属性的条目(在您的示例中是“city”)只出现一次|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2052494|module.exports+=+(array,+prop)+=>+{
+++const+keyValueArray+=+array.map(entry+=>+[entry[prop],+entry]);
+++const+map+=+new+Map(keyValueArray);
+++return+Array.from(map.values());
};|code-block|syntax|javascript|2052495|更多关于地图和数组对象这里的信息|offset|length|2052496|Codepen的基本实例|2052497|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#Relation_with_Array_objects|1|https://codepen.io/anon/pen/QmbpyE?editors=0011^0|0|0|B|2|0|0|0|C|1|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|K|3|L|5|6|7|12|8|@]|9|@$I|13|J|14|1|15]]|A|$]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]|U|$5|P|Q|R|A|$S|V]]]]

You could use a Map so the entries with the same key property (in your case 'city') only appear once

<pre><code>module.exports = (array, prop) =&gt; {
 const keyValueArray = array.map(entry =&gt; [entry[prop], entry]);
 const map = new Map(keyValueArray);
 return Array.from(map.values());
};
</code></pre>

More info about Map and array objects <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#Relation_with_Array_objects" rel="nofollow noreferrer">here</a>

<a href="https://codepen.io/anon/pen/QmbpyE?editors=0011" rel="nofollow noreferrer">Basic example on Codepen</a>

blocks|key|2052521|text|另一种选择：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2052522|const+uniqueBy+=+prop+=>+list+=>+{
++++const+uniques+=+{}
++++return+list.reduce(
++++++++(result,+item)+=>+{
++++++++++++if+(uniques[item[prop]])+return+result
++++++++++++uniques[item[prop]]+=+item
++++++++++++return+[...result,+item]
++++++++},
++++++++[],
++++)
}

const+uniqueById+=+uniqueBy('id')

uniqueById([
++++{+id:+1,+name:+'one'+},
++++{+id:+2,+name:+'two'+},
++++{+id:+1,+name:+'one'+},
++++{+id:+3,+name:+'three'+}
])|code-block|syntax|javascript|2052523|您可以将其粘贴到您的控制台上，以确保其正常工作。它应适用于所提出的设想和其他一些情况。|2052524|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Another option:

<pre><code>const uniqueBy = prop =&gt; list =&gt; {
 const uniques = {}
 return list.reduce(
 (result, item) =&gt; {
 if (uniques[item[prop]]) return result
 uniques[item[prop]] = item
 return [...result, item]
 },
 [],
 )
}

const uniqueById = uniqueBy('id')

uniqueById([
 { id: 1, name: 'one' },
 { id: 2, name: 'two' },
 { id: 1, name: 'one' },
 { id: 3, name: 'three' }
])
</code></pre>

You can paste it on your console to see it working.
It should work for the scenario presented and a few others.

blocks|key|976030|text|在简单的Javascript代码中，从places数组列表中删除重复的城市是|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|976031|var+places+=+[{+'lat':+12.123,+'lng':+13.213,+'city':+"New+York"},
++++++++++++++++{+'lat':+3.123,+'lng':+2.213,+'city':+"New+York"},
++++++++++++++++{+'lat':+43.123,+'lng':+12.213,+'city':+"London"}];
var+unique+=+[];
var+tempArr+=+[];
places.forEach((value,+index)+=>+{
++++if+(unique.indexOf(value.city)+===+-1)+{
++++++++unique.push(value.city);
++++}+else+{
++++++++tempArr.push(index);++++
++++}
});
tempArr.reverse();
tempArr.forEach(ele+=>+{
++++places.splice(ele,+1);
});
console.log(places);|code-block|syntax|javascript|976032|entityMap^0|4|A|J|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

In simple <code>Javascript</code> code to remove duplicate cities from <code>places</code> array list is

<pre><code>var places = [{ 'lat': 12.123, 'lng': 13.213, 'city': "New York"},
 { 'lat': 3.123, 'lng': 2.213, 'city': "New York"},
 { 'lat': 43.123, 'lng': 12.213, 'city': "London"}];
var unique = [];
var tempArr = [];
places.forEach((value, index) =&gt; {
 if (unique.indexOf(value.city) === -1) {
 unique.push(value.city);
 } else {
 tempArr.push(index); 
 }
});
tempArr.reverse();
tempArr.forEach(ele =&gt; {
 places.splice(ele, 1);
});
console.log(places);
</code></pre>

blocks|key|976069|text|基于以上https://stackoverflow.com/a/18773857/49564的通用打字本答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|976070|export+function+isDistinct<T>(mapper:+(value:+T)+=>+string):+(value:+T)+=>+boolean+{
++const+keys:+{+[index:+string]:+boolean+}+=+{};

++return+(entry:+T)+=>+{
++++const+key+=+mapper(entry);

++++if+(keys[key]+!==+undefined)+{
++++++return+false;
++++}

++++return+keys[key]+=+true;
++};
}

//+Usage+example:
const+items+=+[+{+id:+1+},+{+id:+2+},+{+id:+3+},+{+id:+1+}+];
const+unique+=+items.filter(isDistinct(i+=>+i.id));|code-block|syntax|javascript|976071|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/18773857/49564^0|4|16|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Generic Typescript answer based on <a href="https://stackoverflow.com/a/18773857/49564">https://stackoverflow.com/a/18773857/49564</a> above:

<pre><code>export function isDistinct&lt;T&gt;(mapper: (value: T) =&gt; string): (value: T) =&gt; boolean {
 const keys: { [index: string]: boolean } = {};

 return (entry: T) =&gt; {
 const key = mapper(entry);

 if (keys[key] !== undefined) {
 return false;
 }

 return keys[key] = true;
 };
}

// Usage example:
const items = [ { id: 1 }, { id: 2 }, { id: 3 }, { id: 1 } ];
const unique = items.filter(isDistinct(i =&gt; i.id));
</code></pre>

blocks|key|64225|text|我想你想要这个，|type|unstyled|depth|inlineStyleRanges|entityRanges|data|64226|注意：不需要库。|offset|length|style|BOLD|64227|let+array+=+[{+id:+1},+{id:+2},+{id:+3}];

function+addUniqeObj(data)+{
++let+index+=+-1;

++for(let+i+=+0,+i+<+array.length;+i%2B%2B)+{
++++if(array[i].id+===+data.id)+{
++++++index+=+i;
++++}
++}

++if(index+>+-1)+{
++++array[index]+=+data;
++}+else+{
++++array.push(data)
++}

}|code-block|syntax|javascript|64228|entityMap^0|0|0|3|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|S|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I think you want this,

NOTE: No library is required.

<pre><code>let array = [{ id: 1}, {id: 2}, {id: 3}];

function addUniqeObj(data) {
 let index = -1;

 for(let i = 0, i &lt; array.length; i++) {
 if(array[i].id === data.id) {
 index = i;
 }
 }

 if(index &gt; -1) {
 array[index] = data;
 } else {
 array.push(data)
 }

}
</code></pre>

blocks|key|64236|text|我们可以使用JavaScript+地图通过任何属性创建唯一对象的列表。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|64237|例如：|64238|​|64239|var+places+=+[{+'lat':+12.123,+'lng':+13.213,+'city':+"New+York"},
++++++++++++++++{+'lat':+3.123,+'lng':+2.213,+'city':+"New+York"},
++++++++++++++++{+'lat':+43.123,+'lng':+12.213,+'city':+"London"}];
++++++++++++++++
var+cityMap+=+new+Map();
places.forEach(p=>+cityMap.set(p.city,+p));

console.log([...cityMap.values()]);|code-block|syntax|javascript|64240|64241|执行代码段以查看结果。|64242|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map^0|H|2|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|6|7|11|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|12|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|13|8|@]|9|@]|C|$K|L]]|$1|M|3|G|5|6|7|14|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|15|8|@]|9|@]|C|$]]|$1|P|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|Q|$R|$5|S|T|U|C|$V|W]]]]

We can create the list of unique objects by any property using JavaScript <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map" rel="nofollow noreferrer">Map</a>.

For example :

<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var places = [{ 'lat': 12.123, 'lng': 13.213, 'city': "New York"},
 { 'lat': 3.123, 'lng': 2.213, 'city': "New York"},
 { 'lat': 43.123, 'lng': 12.213, 'city': "London"}];
 
var cityMap = new Map();
places.forEach(p=&gt; cityMap.set(p.city, p));

console.log([...cityMap.values()]);</code></pre>
</div>
</div>


Execute code snippet to see the result.

blocks|key|976108|text|拉斐尔比登方法的另一个变体是：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|976109|​|976110|const+dedupExample+=+[
++++{id:+1,+c:+'whatever'},
++++{id:+1,+c:+'1whatever'},
++++{id:+2,+c:+'2whatever'},
++++{id:+2,+c:+'2whatever'},
++++{id:+3,+c:+'2whatever'},
]

const+getUniqueBy+=+(prop,+list)+=>+{
++++const+objUniq+=+list.reduce((res,+item)+=>+({+...res,+[item[prop]]:+item+}),+{})
++++return+Object.keys(objUniq).map(item+=>+objUniq[item])
}

const+uniq+=+getUniqueBy('id',+dedupExample)

console.info('info',+{+uniq+})
+++/*+[
++++{id:+1,+c:+'whatever'},
++++{id:+2,+c:+'2whatever'},
++++{id:+3,+c:+'2whatever'},
++]+*/|code-block|syntax|javascript|976111|976112|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/53546709/4791116^0|0|5|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|Y|8|@]|9|@]|C|$I|J]]|$1|K|3|E|5|6|7|Z|8|@]|9|@]|C|$]]|$1|L|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|M|$N|$5|O|P|Q|C|$R|S]]]]

Another variation of the <a href="https://stackoverflow.com/a/53546709/4791116">rafaelbiten</a> approach:
<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const dedupExample = [
 {id: 1, c: 'whatever'},
 {id: 1, c: '1whatever'},
 {id: 2, c: '2whatever'},
 {id: 2, c: '2whatever'},
 {id: 3, c: '2whatever'},
]

const getUniqueBy = (prop, list) =&gt; {
 const objUniq = list.reduce((res, item) =&gt; ({ ...res, [item[prop]]: item }), {})
 return Object.keys(objUniq).map(item =&gt; objUniq[item])
}

const uniq = getUniqueBy('id', dedupExample)

console.info('info', { uniq })
 /* [
 {id: 1, c: 'whatever'},
 {id: 2, c: '2whatever'},
 {id: 3, c: '2whatever'},
 ] */</code></pre>
</div>
</div>

blocks|key|64249|text|您可以使用filter使用Set，方法是只包含属性值尚未添加到Set+(之后应该添加到Set)的元素。这可以使用逻辑和运算符(&&)在一行中完成。使用这种数据结构具有次线性查找次数(通常为O(1))的优点。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|64250|下面是一个通用函数，用于根据特定属性(prop)从对象数组(arr)获得唯一的对象数组。注意，在重复的情况下，只保留具有属性值的第一个对象。|64251|const+getUniqueBy+=+(arr,+prop)+=>+{
++const+set+=+new+Set;
++return+arr.filter(o+=>+!set.has(o[prop])+&&+set.add(o[prop]));
};|code-block|syntax|javascript|64252|演示：|64253|​|64254|var+places+=+[{
++lat:+12.123,
++lng:+13.213,
++city:+'New+York'
},+{
++lat:+3.123,
++lng:+2.213,
++city:+'New+York'
},+{
++lat:+3.123,
++lng:+4.123,
++city:+'Some+City'
}];
const+getUniqueBy+=+(arr,+prop)+=>+{
++const+set+=+new+Set;
++return+arr.filter(o+=>+!set.has(o[prop])+&&+set.add(o[prop]));
};
console.log(getUniqueBy(places,+'city'));|64255|64256|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set^0|5|6|D|3|V|3|17|3|1R|2|2M|4|5|6|0|D|3|1|0|J|4|U|3|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]]|D|@$9|1G|A|1H|1|1I]|$9|1J|A|1K|1|1L]]|E|$]]|$1|F|3|G|5|6|7|1M|8|@$9|1N|A|1O|B|C]|$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1R|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1S|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1T|8|@]|D|@]|E|$]]|$1|Q|3|R|5|J|7|1U|8|@]|D|@]|E|$K|L]]|$1|S|3|P|5|6|7|1V|8|@]|D|@]|E|$]]|$1|T|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|U|$V|$5|W|X|Y|E|$Z|10]]|11|$5|W|X|Y|E|$Z|12]]]]

You can <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter" rel="nofollow noreferrer"><code>filter</code></a> using a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set" rel="nofollow noreferrer"><code>Set</code></a> by only including elements with a property value that has not yet been added to the <code>Set</code> (after which it should be added to the <code>Set</code>). This can be accomplished in one line using the logical and operator (<code>&amp;&amp;</code>). Using this data structure has the advantage of sublinear lookup times (often <code>O(1)</code>).
Below is a general function to obtain a unique array of objects based on a specific property (<code>prop</code>) from an array of objects (<code>arr</code>). Note that in the case of duplicates, only the first object with the property value will be retained.
<pre><code>const getUniqueBy = (arr, prop) =&gt; {
 const set = new Set;
 return arr.filter(o =&gt; !set.has(o[prop]) &amp;&amp; set.add(o[prop]));
};
</code></pre>
Demo:
<div class="snippet" data-lang="js" data-hide="true" data-console="true" data-babel="false">
<div class="snippet-code snippet-currently-hidden">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var places = [{
 lat: 12.123,
 lng: 13.213,
 city: 'New York'
}, {
 lat: 3.123,
 lng: 2.213,
 city: 'New York'
}, {
 lat: 3.123,
 lng: 4.123,
 city: 'Some City'
}];
const getUniqueBy = (arr, prop) =&gt; {
 const set = new Set;
 return arr.filter(o =&gt; !set.has(o[prop]) &amp;&amp; set.add(o[prop]));
};
console.log(getUniqueBy(places, 'city'));</code></pre>
</div>
</div>

blocks|key|2052657|text|const+distinctArrayByCity=+[
++++...new+Map(array.map((item)+=>+[item.city,+item])).values(),
];|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2052658|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>const distinctArrayByCity= [
 ...new Map(array.map((item) =&gt; [item.city, item])).values(),
];
</code></pre>

I created an array of objects like so:
<pre class="lang-js prettyprint-override"><code>[
 {
 &quot;lat&quot;: 12.123,
 &quot;lng&quot;: 13.213,
 &quot;city&quot;: &quot;New York&quot;
 },
 {
 &quot;lat&quot;: 3.123,
 &quot;lng&quot;: 2.213,
 &quot;city&quot;: &quot;New York&quot;
 },
 {
 &quot;lat&quot;: 1.513,
 &quot;lng&quot;: 1.113,
 &quot;city&quot;: &quot;London&quot;
 }
]
</code></pre>
I'm trying to create a new array that filters the <code>places</code> to only contains objects that don't have the same <code>city</code> property (lat/lng duplicates are ok). Is there a built in JS or Jquery function to achieve this?

Create array of unique objects by property

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我创建了一个像这样的对象数组：[    {        "lat": 12.123,        "lng": 13.213,        "city": "New York"    },    {        "lat": 3.123,        "lng": 2.213,        "city": ...

问按属性创建唯一对象数组
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问按属性创建唯一对象数组EN