entityMap|blocks|key|1k1el|text|您可以使用数组和indexOf：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|d0tge|if+([1,3,12].indexOf(foo)+>+-1)|code-block|syntax|javascript^0|8|7|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@$A|M|B|N|C|D]]|E|@]|F|$]]|$2|G|4|H|6|I|8|O|9|@]|E|@]|F|$J|K]]]]

You could use an array and <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/indexOf" rel="noreferrer"><code>indexOf</code></a>:

<pre><code>if ([1,3,12].indexOf(foo) &gt; -1)
</code></pre>

entityMap|blocks|key|fieih|text|var+a+=+[1,2,3];

if+(+a.indexOf(+1+)+!==+-1+)+{+}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|cklo8|请注意，indexOf不在核心ECMAScript中。你需要有一个IE的代码片段，可能还有其他不支持Array.prototype.indexOf的浏览器。|unstyled|b8p9t|if+(!Array.prototype.indexOf)
{
++Array.prototype.indexOf+=+function(searchElement+/*,+fromIndex+*/)
++{
++++"use+strict";

++++if+(this+===+void+0+%7C%7C+this+===+null)
++++++throw+new+TypeError();

++++var+t+=+Object(this);
++++var+len+=+t.length+>>>+0;
++++if+(len+===+0)
++++++return+-1;

++++var+n+=+0;
++++if+(arguments.length+>+0)
++++{
++++++n+=+Number(arguments[1]);
++++++if+(n+!==+n)
++++++++n+=+0;
++++++else+if+(n+!==+0+&&+n+!==+(1+/+0)+&&+n+!==+-(1+/+0))
++++++++n+=+(n+>+0+%7C%7C+-1)+*+Math.floor(Math.abs(n));
++++}

++++if+(n+>=+len)
++++++return+-1;

++++var+k+=+n+>=+0
++++++++++?+n
++++++++++:+Math.max(len+-+Math.abs(n),+0);

++++for+(;+k+<+len;+k%2B%2B)
++++{
++++++if+(k+in+t+&&+t[k]+===+searchElement)
++++++++return+k;
++++}
++++return+-1;
++};
}^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$C|D]]|$2|E|4|F|6|G|8|K|9|@]|A|@]|B|$]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$C|D]]]]

<pre><code>var a = [1,2,3];

if ( a.indexOf( 1 ) !== -1 ) { }
</code></pre>

Note that indexOf is not in the core ECMAScript. You'll need to have a snippet for IE and possibly other browsers that dont support Array.prototype.indexOf.

<pre><code>if (!Array.prototype.indexOf)
{
 Array.prototype.indexOf = function(searchElement /*, fromIndex */)
 {
 "use strict";

 if (this === void 0 || this === null)
 throw new TypeError();

 var t = Object(this);
 var len = t.length &gt;&gt;&gt; 0;
 if (len === 0)
 return -1;

 var n = 0;
 if (arguments.length &gt; 0)
 {
 n = Number(arguments[1]);
 if (n !== n)
 n = 0;
 else if (n !== 0 &amp;&amp; n !== (1 / 0) &amp;&amp; n !== -(1 / 0))
 n = (n &gt; 0 || -1) * Math.floor(Math.abs(n));
 }

 if (n &gt;= len)
 return -1;

 var k = n &gt;= 0
 ? n
 : Math.max(len - Math.abs(n), 0);

 for (; k &lt; len; k++)
 {
 if (k in t &amp;&amp; t[k] === searchElement)
 return k;
 }
 return -1;
 };
}
</code></pre>

entityMap|blocks|key|7i0qd|text|这很容易扩展和阅读：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|33sns|switch+(foo)+{
++++case+1:
++++case+3:
++++case+12:
++++++++//+...
++++++++break

++++case+4:
++++case+5:
++++case+6:
++++++++//+something+else
++++++++break
}|code-block|syntax|javascript|2tpu2|但不一定更容易:)^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|J|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|K|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|L|9|@]|A|@]|B|$]]]]

This is easily extendable and readable:

<pre><code>switch (foo) {
 case 1:
 case 3:
 case 12:
 // ...
 break

 case 4:
 case 5:
 case 6:
 // something else
 break
}
</code></pre>

But not necessarily easier :)

entityMap|blocks|key|1qvur|text|你可以写if(foo+in+L(10,20,30))如果您定义L要成为|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|faa91|var+L+=+function()
{
++++var+obj+=+{};
++++for(var+i=0;+i|code-block|syntax|javascript^0|4|M|V|1|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@$A|M|B|N|C|D]|$A|O|B|P|C|D]]|E|@]|F|$]]|$2|G|4|H|6|I|8|Q|9|@]|E|@]|F|$J|K]]]]

You can write <code>if(foo in L(10,20,30))</code> if you define <code>L</code> to be

<pre><code>var L = function()
{
 var obj = {};
 for(var i=0; i&lt;arguments.length; i++)
 obj[arguments[i]] = null;

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

entityMap|blocks|key|3fqbc|text|使用提供的答案，我得到了以下结论：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|55th9|Object.prototype.in+=+function()+{
++++for(var+i=0;+i|code-block|syntax|javascript|9om2p|It+can+be+called+like:|offset|length|style|CODE|fleq8|if(foo.in(1,+3,+12))+{
++++//+...
}|ef43a|Edit:+I+came+across+this+'trick'+lately+which+is+useful+if+the+values+are+strings+and+do+not+contain+special+characters.+For+special+characters+is+becomes+ugly+due+to+escaping+and+is+also+more+error-prone+due+to+that.|f96sp|/foo%7Cbar%7Csomething/.test(str);|1i70i|To+be+more+precise,+this+will+check+the+exact+string,+but+then+again+is+more+complicated+for+a+simple+equality+test:|2qlaq|/%5E(foo%7Cbar%7Csomething)$/.test(str);^0|0|0|0|M|0|0|0|61|0|0|0|38|0^^$0|$]|1|@$2|3|4|5|6|7|8|X|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|Y|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|Z|9|@$J|10|K|11|L|M]]|A|@]|B|$]]|$2|N|4|O|6|E|8|12|9|@]|A|@]|B|$F|G]]|$2|P|4|Q|6|7|8|13|9|@$J|14|K|15|L|M]]|A|@]|B|$]]|$2|R|4|S|6|E|8|16|9|@]|A|@]|B|$F|G]]|$2|T|4|U|6|7|8|17|9|@$J|18|K|19|L|M]]|A|@]|B|$]]|$2|V|4|W|6|E|8|1A|9|@]|A|@]|B|$F|G]]]]

Using the answers provided, I ended up with the following:

<pre><code>Object.prototype.in = function() {
 for(var i=0; i&lt;arguments.length; i++)
 if(arguments[i] == this) return true;
 return false;
}
</code></pre>

It can be called like:

<pre><code>if(foo.in(1, 3, 12)) {
 // ...
}
</code></pre>

<hr>

Edit: I came across this 'trick' lately which is useful if the values are strings and do not contain special characters. For special characters is becomes ugly due to escaping and is also more error-prone due to that.

<pre><code>/foo|bar|something/.test(str);
</code></pre>

To be more precise, this will check the exact string, but then again is more complicated for a simple equality test:

<pre><code>/^(foo|bar|something)$/.test(str);
</code></pre>

entityMap|blocks|key|229mq|text|我喜欢被接受的答案，但我认为让它也能接受数组会很巧妙，所以我将其扩展为：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2m01a|Object.prototype.isin+=+function()+{
++++for(var+i+=+arguments.length;+i--;)+{
++++++++var+a+=+arguments[i];
++++++++if(a.constructor+===+Array)+{
++++++++++++for(var+j+=+a.length;+j--;)
++++++++++++++++if(a[j]+==+this)+return+true;
++++++++}
++++++++else+if(a+==+this)+return+true;
++++}
++++return+false;
}

var+lucky+=+7,
++++more+=+[7,+11,+42];
lucky.isin(2,+3,+5,+8,+more)+//true|code-block|syntax|javascript|640i2|您可以通过更改==至===。|offset|length|style|CODE^0|0|0|7|2|A|3^^$0|$]|1|@$2|3|4|5|6|7|8|N|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|O|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|P|9|@$J|Q|K|R|L|M]|$J|S|K|T|L|M]]|A|@]|B|$]]]]

I liked the accepted answer, but thought it would be neat to enable it to take arrays as well, so I expanded it to this:

<pre><code>Object.prototype.isin = function() {
 for(var i = arguments.length; i--;) {
 var a = arguments[i];
 if(a.constructor === Array) {
 for(var j = a.length; j--;)
 if(a[j] == this) return true;
 }
 else if(a == this) return true;
 }
 return false;
}

var lucky = 7,
 more = [7, 11, 42];
lucky.isin(2, 3, 5, 8, more) //true
</code></pre>

You can remove type coercion by changing <code>==</code> to <code>===</code>.

entityMap|blocks|key|h01c|text|如果您有权使用下划线，则可以使用以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|6790d|if+(_.contains([1,+3,+12],+foo))+{
++//+...
}|code-block|syntax|javascript|adf6d|曾经在Lodash中工作过(在V4之前)，现在你必须使用|6mnl0|if+(_.includes([1,+3,+12],+foo))+{
++handleYellowFruit();
}^0|0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|L|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|M|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|N|9|@]|A|@]|B|$]]|$2|J|4|K|6|E|8|O|9|@]|A|@]|B|$F|G]]]]

If you have access to Underscore, you can use the following:

<pre><code>if (_.contains([1, 3, 12], foo)) {
 // ...
}
</code></pre>

<code>contains</code> used to work in Lodash as well (prior to V4), now you have to use <code>includes</code>

<pre><code>if (_.includes([1, 3, 12], foo)) {
 handleYellowFruit();
}
</code></pre>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/includes|blocks|key|cp69n|text|在ECMA2016中，您可以使用包括方法。这是我见过的最干净的方式。(所有主要浏览器都支持)|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|43m0s|if([1,3,12].includes(foo))+{
++++//+...
}|code-block|syntax|javascript^0|G|2|0|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|P|G|@]|H|@$I|Q|J|R|A|S]]|6|$]]|$A|K|C|L|2|M|F|T|G|@]|H|@]|6|$N|O]]]]

In ECMA2016 you can use the <a href="https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/includes" rel="noreferrer">includes</a> method. It's the cleanest way I've seen. (Supported by all major browsers)
<pre><code>if([1,3,12].includes(foo)) {
 // ...
}
</code></pre>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set|blocks|key|4lqeu|text|此外，由于检查结果所依据的值都是唯一的，因此可以使用Set.prototype.has()还有。​|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|adj6k|var+valid+=+[1,+3,+12];
var+goodFoo+=+3;
var+badFoo+=+55;

//+Test
console.log(+new+Set(valid).has(goodFoo)+);
console.log(+new+Set(valid).has(badFoo)+);|code-block|syntax|javascript|2cvns|​^0|Q|J|0|0|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|R|G|@]|H|@$I|S|J|T|A|U]]|6|$]]|$A|K|C|L|2|M|F|V|G|@]|H|@]|6|$N|O]]|$A|P|C|Q|2|E|F|W|G|@]|H|@]|6|$]]]]

Also, since the values against which you're checking the result are all unique you can use the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set" rel="nofollow noreferrer">Set.prototype.has()</a> as well. 

<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 valid = [1, 3, 12];
var goodFoo = 3;
var badFoo = 55;

// Test
console.log( new Set(valid).has(goodFoo) );
console.log( new Set(valid).has(badFoo) );</code></pre>
</div>
</div>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://api.jquery.com/jQuery.inArray/|blocks|key|6hi57|text|我简单地使用了jQueryinArray函数和一个值数组来完成此操作：|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|eqpj|myArr+=+["A",+"B",+"C",+"C-"];

var+test+=+$.inArray("C",+myArr)++
//+returns+index+of+2+returns+-1+if+not+in+array

if(test+>=+0)+//+true|code-block|syntax|javascript^0|D|7|0|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|P|G|@]|H|@$I|Q|J|R|A|S]]|6|$]]|$A|K|C|L|2|M|F|T|G|@]|H|@]|6|$N|O]]]]

I simply used jQuery <a href="https://api.jquery.com/jQuery.inArray/" rel="nofollow noreferrer">inArray</a> function and an array of values to accomplish this:

<pre><code>myArr = ["A", "B", "C", "C-"];

var test = $.inArray("C", myArr) 
// returns index of 2 returns -1 if not in array

if(test &gt;= 0) // true
</code></pre>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match#Browser_compatibility|blocks|key|5vapc|text|对于后代，您可能希望使用正则表达式作为替代。对浏览器的支持也很好(参考https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match#浏览器_兼容性)|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|dp5un|试试这个|46dft|if+(foo.toString().match(/%5E(1%7C3%7C12)$/))+{
++++document.write('Regex+me+IN
');
}+else+{
++++document.write('Regex+me+OUT
');
}|code-block|syntax|javascript^0|Z|2T|0|0|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|R|G|@]|H|@$I|S|J|T|A|U]]|6|$]]|$A|K|C|L|2|E|F|V|G|@]|H|@]|6|$]]|$A|M|C|N|2|O|F|W|G|@]|H|@]|6|$P|Q]]]]

For posterity you might want to use regular expressions as an alternative. Pretty good browser support as well (ref. <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match#Browser_compatibility" rel="nofollow noreferrer">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match#Browser_compatibility</a>)

Try this

<pre class="lang-js prettyprint-override"><code>if (foo.toString().match(/^(1|3|12)$/)) {
 document.write('Regex me IN&lt;br&gt;');
} else {
 document.write('Regex me OUT&lt;br&gt;');
}
</code></pre>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some|blocks|key|e06j4|text|这是一个小辅助箭头函数：|unstyled|depth|inlineStyleRanges|entityRanges|cnokl|const+letters+=+['A',+'B',+'C',+'D'];

function+checkInList(arr,+val)+{
++return+arr.some(arrVal+=>+val+===+arrVal);
}

checkInList(letters,+'E');+++//+false
checkInList(letters,+'A');+++//+true|code-block|syntax|javascript|540c8|更多信息在这里...|offset|length^0|0|0|0|A|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|R|G|@]|H|@]|6|$]]|$A|I|C|J|2|K|F|S|G|@]|H|@]|6|$L|M]]|$A|N|C|O|2|E|F|T|G|@]|H|@$P|U|Q|V|A|W]]|6|$]]]]

This is a little helper arrow function:
<pre><code>const letters = ['A', 'B', 'C', 'D'];

function checkInList(arr, val) {
 return arr.some(arrVal =&gt; val === arrVal);
}

checkInList(letters, 'E'); // false
checkInList(letters, 'A'); // true
</code></pre>
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some" rel="nofollow noreferrer">More info here...</a>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes|blocks|key|fn3kf|text|现在你可能有一个更好的解决方案来解决这种情况，但我更喜欢的其他方式。|unstyled|depth|inlineStyleRanges|entityRanges|2c195|const+arr+=+[1,3,12]
if(+arr.includes(foo))+{+//+it+will+return+true+if+you+`foo`+is+one+of+array+values+else+false
++//+code+here++++
}|code-block|syntax|javascript|bl55d|我更喜欢上面的解决方案，而不是indexOf检查，在那里你也需要检查索引。|a48b5|包括文档|offset|length|f0j|if+(+arr.indexOf(+foo+)+!==+-1+)+{+}^0|0|0|0|0|4|0|0^^$0|$1|$2|3|4|5|6|$7|8]]]|9|@$A|B|C|D|2|E|F|V|G|@]|H|@]|6|$]]|$A|I|C|J|2|K|F|W|G|@]|H|@]|6|$L|M]]|$A|N|C|O|2|E|F|X|G|@]|H|@]|6|$]]|$A|P|C|Q|2|E|F|Y|G|@]|H|@$R|Z|S|10|A|11]]|6|$]]|$A|T|C|U|2|K|F|12|G|@]|H|@]|6|$L|M]]]]

Now you may have a better solution to resolve this scenario, but other way which i preferred.

<pre><code>const arr = [1,3,12]
if( arr.includes(foo)) { // it will return true if you `foo` is one of array values else false
 // code here 
}
</code></pre>

I preferred above solution over the indexOf check where you need to check index as well.

<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes" rel="noreferrer">includes docs</a>

<pre><code>if ( arr.indexOf( foo ) !== -1 ) { }
</code></pre>

I'm checking a variable, say <code>foo</code>, for equality to a number of values. For example,

<pre><code>if( foo == 1 || foo == 3 || foo == 12 ) {
 // ...
}
</code></pre>

The point is that it is rather much code for such a trivial task. I came up with the following:

<pre><code>if( foo in {1: 1, 3: 1, 12: 1} ) {
 // ...
}
</code></pre>

but also this does not completely appeal to me, because I have to give redundant values to the items in the object.

Does anyone know a decent way of doing an equality check against multiple values?

Check variable equality against a list of values

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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 我在检查一个变量，比如说foo，表示与多个值相等。例如， if( foo == 1 || foo == 3 || foo == 12 ) {    // ...} 重点是，对于这样一个微不足道的任务，这是相当多的代码。我想出了以下几点： if( foo in {1: 1, 3: 1, 12: 1} ) {    //...

问根据值列表检查变量相等性
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