blocks|key|1004700|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1004701|var+obj+=+{
++key1:+'value1',
++key2:+'value2',
++key3:+'value3',
++key4:+'value4'
};
var+keys+=+[];

for+(var+k+in+obj)+keys.push(k);

console.log("total+"+%2B+keys.length+%2B+"+keys:+"+%2B+keys);|code-block|syntax|javascript|1004702|1004703|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|K|8|@]|9|@]|A|$E|F]]|$1|G|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|M|8|@]|9|@]|A|$]]]|I|$]]

<p><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 obj = {
  key1: 'value1',
  key2: 'value2',
  key3: 'value3',
  key4: 'value4'
};
var keys = [];

for (var k in obj) keys.push(k);

console.log("total " + keys.length + " keys: " + keys);</code></pre>
</div>
</div>
</p>


blocks|key|1219137|text|var+keys+=+new+Array();
for(var+key+in+obj)
{
+++keys[keys.length]+=+key;
}

var+keyLength+=+keys.length;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1219138|要访问对象中的任意值，可以使用objkey；|unstyled|1219139|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>var keys = new Array();
for(var key in obj)
{
   keys[keys.length] = key;
}

var keyLength = keys.length;
</code></pre>

<p>to access any value from the object, you can use obj[key];</p>


blocks|key|1219162|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1219163|var+obj+=+{
+++key1:+'value1',
+++key2:+'value2',
+++key3:+'value3',
+++key4:+'value4'
}
var+keys+=+Object.keys(obj);
console.log('obj+contains+'+%2B+keys.length+%2B+'+keys:+'%2B++keys);|code-block|syntax|javascript|1219164|1219165|现在在大多数主流浏览器上都是supported。|offset|length|1219166|entityMap|0|LINK|mutability|MUTABLE|url|http://kangax.github.com/es5-compat-table/^0|0|0|0|E|9|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|G|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@]|9|@$J|X|K|Y|1|Z]]|A|$]]|$1|L|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|S]]]]

<p><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 obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
}
var keys = Object.keys(obj);
console.log('obj contains ' + keys.length + ' keys: '+  keys);</code></pre>
</div>
</div>
</p>

<p>It's <a href="http://kangax.github.com/es5-compat-table/" rel="noreferrer">supported</a> on most major browsers now.</p>


blocks|key|1219211|text|如果您只需要特定于该特定对象的键，而不需要任何派生的prototype属性：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1219212|function+getKeys(obj)+{
++++var+r+=+[]
++++for+(var+k+in+obj)+{
++++++++if+(!obj.hasOwnProperty(k))+
++++++++++++continue
++++++++r.push(k)
++++}
++++return+r
}|code-block|syntax|javascript|1219213|例如：|1219214|var+keys+=+getKeys({'eggs':+null,+'spam':+true})
var+length+=+keys.length+//+access+the+`length`+property+as+usual+for+arrays|1219215|entityMap^0|Q|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

<p>If you only want the keys which are specific to that particular object and not any derived <code>prototype</code> properties:</p>

<pre><code>function getKeys(obj) {
    var r = []
    for (var k in obj) {
        if (!obj.hasOwnProperty(k)) 
            continue
        r.push(k)
    }
    return r
}
</code></pre>

<p>e.g:</p>

<pre><code>var keys = getKeys({'eggs': null, 'spam': true})
var length = keys.length // access the `length` property as usual for arrays
</code></pre>


blocks|key|1219245|text|obj+=+{'a':'c','b':'d'}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1219246|您可以尝试：|unstyled|1219247|[index+for+(index+in+obj)]+|1219248|这将返回：|1219249|['a','b']|1219250|获取密钥列表，或者|1219251|[obj[index]+for+(index+in+obj)]|1219252|要获取值，请执行以下操作|1219253|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$B|C]]|$1|M|3|N|5|F|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$B|C]]|$1|Q|3|R|5|F|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|F|7|12|8|@]|9|@]|A|$]]]|T|$]]

<pre><code>obj = {'a':'c','b':'d'}
</code></pre>

<p>You can try: </p>

<pre><code>[index for (index in obj)] 
</code></pre>

<p>this will return:</p>

<pre><code>['a','b']
</code></pre>

<p>to get the list of keys
or </p>

<pre><code>[obj[index] for (index in obj)]
</code></pre>

<p>to get the values</p>


blocks|key|1219286|text|Underscore.js使转换变得非常干净：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1219287|var+keys+=+_.map(x,+function(v,+k)+{+return+k;+});|code-block|syntax|javascript|1219288|编辑:我错过了你也可以这样做：|1219289|var+keys+=+_.keys(x);|1219290|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<p>Underscore.js makes the transformation pretty clean:</p>

<pre><code>var keys = _.map(x, function(v, k) { return k; });
</code></pre>

<p>Edit: I missed that you can do this too:</p>

<pre><code>var keys = _.keys(x);
</code></pre>


blocks|key|1004983|text|请注意，在coffeescript中，这可以在所有浏览器和节点中完成，如|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1004984|k+for+k+of+obj|code-block|syntax|javascript|1004985|因此|1004986|(1+for+_+of+obj).length|1004987|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<p>Note that in coffeescript this can be accomplished in all browsers and node as</p>

<pre><code>k for k of obj
</code></pre>

<p>and thus</p>

<pre><code>(1 for _ of obj).length
</code></pre>


blocks|key|1219358|text|使用slice、apply和join方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1219359|var+print+=+Array.prototype.slice.apply(+obj+);
alert('length='%2Bprint.length%2B'+list'%2Bprint.join());|code-block|syntax|javascript|1219360|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>using slice, apply and join method.</p>

<pre><code>var print = Array.prototype.slice.apply( obj );
alert('length='+print.length+' list'+print.join());
</code></pre>


blocks|key|1219383|text|对于列出JSON对象键的逗号分隔字符串，请尝试以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1219384|function+listKeys(jObj){
++++var+keyString+=+'';
++++for(var+k+in+jObj){
++++++++keyString%2B=(','%2Bk);
++++}
++++return+keyString.slice(1);
}



/*+listKeys({'a'+:+'foo',+'b'+:+'foo',+'c'+:+'foo'})+->+'a,b,c'+*/|code-block|syntax|javascript|1219385|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>For a comma-delineated string listing the keys of a JSON Object, try the following:</p>

<pre><code>function listKeys(jObj){
    var keyString = '';
    for(var k in jObj){
        keyString+=(','+k);
    }
    return keyString.slice(1);
}



/* listKeys({'a' : 'foo', 'b' : 'foo', 'c' : 'foo'}) -&gt; 'a,b,c' */
</code></pre>


blocks|key|1219427|text|Anurags的答案基本上是正确的。但是要在较旧的浏览器中也支持Object.keys(obj)，您可以使用从https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys复制的以下代码。如果在浏览器中不可用，它会添加Object.keys(obj)方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1219428|if+(!Object.keys)+{
+Object.keys+=+(function()+{
+'use+strict';
+var+hasOwnProperty+=+Object.prototype.hasOwnProperty,
++++hasDontEnumBug+=+!({+toString:+null+}).propertyIsEnumerable('toString'),
++++dontEnums+=+[
++++++'toString',
++++++'toLocaleString',
++++++'valueOf',
++++++'hasOwnProperty',
++++++'isPrototypeOf',
++++++'propertyIsEnumerable',
++++++'constructor'
++++],
++++dontEnumsLength+=+dontEnums.length;

return+function(obj)+{
++if+(typeof+obj+!==+'object'+&&+(typeof+obj+!==+'function'+%7C%7C+obj+===+null))+{
++++throw+new+TypeError('Object.keys+called+on+non-object');
++}

++var+result+=+[],+prop,+i;

++for+(prop+in+obj)+{
++++if+(hasOwnProperty.call(obj,+prop))+{
++++++result.push(prop);
++++}
++}

++if+(hasDontEnumBug)+{
++++for+(i+=+0;+i+<+dontEnumsLength;+i%2B%2B)+{
++++++if+(hasOwnProperty.call(obj,+dontEnums[i]))+{
++++++++result.push(dontEnums[i]);
++++++}
++++}
++}
++return+result;
};
}());
}|code-block|syntax|javascript|1219429|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys^0|W|G|4Q|G|1J|2K|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

<p>Anurags answer is basically correct.
But to support <code>Object.keys(obj)</code> in older browsers as well you can use the code below that is copied from 
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys" rel="nofollow">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys</a>
. It adds the <code>Object.keys(obj)</code> method if it's not available from the browser.</p>

<pre><code>if (!Object.keys) {
 Object.keys = (function() {
 'use strict';
 var hasOwnProperty = Object.prototype.hasOwnProperty,
    hasDontEnumBug = !({ toString: null }).propertyIsEnumerable('toString'),
    dontEnums = [
      'toString',
      'toLocaleString',
      'valueOf',
      'hasOwnProperty',
      'isPrototypeOf',
      'propertyIsEnumerable',
      'constructor'
    ],
    dontEnumsLength = dontEnums.length;

return function(obj) {
  if (typeof obj !== 'object' &amp;&amp; (typeof obj !== 'function' || obj === null)) {
    throw new TypeError('Object.keys called on non-object');
  }

  var result = [], prop, i;

  for (prop in obj) {
    if (hasOwnProperty.call(obj, prop)) {
      result.push(prop);
    }
  }

  if (hasDontEnumBug) {
    for (i = 0; i &lt; dontEnumsLength; i++) {
      if (hasOwnProperty.call(obj, dontEnums[i])) {
        result.push(dontEnums[i]);
      }
    }
  }
  return result;
};
}());
}
</code></pre>


blocks|key|1005092|text|支持ECMAScript+5的浏览器的递归解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1005093|var+getObjectKeys+=+function(obj)+{
++++var+keys+=+Object.keys(obj);
++++var+length+=+keys.length;

++++if+(length+!==+0)+{
++++++++for+(var+i+=+0;+i+<+length;+i%2B%2B)+{
++++++++++++if+(typeof+obj[keys[i]]+===+'object')+{
++++++++++++++++keys[keys[i]]+=+getObjectKeys(obj[keys[i]]);
++++++++++++}
++++++++}
++++}

++++return+keys;
};|code-block|syntax|javascript|1005094|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>Recursive solution for browsers that support ECMAScript 5:</p>

<pre><code>var getObjectKeys = function(obj) {
    var keys = Object.keys(obj);
    var length = keys.length;

    if (length !== 0) {
        for (var i = 0; i &lt; length; i++) {
            if (typeof obj[keys[i]] === 'object') {
                keys[keys[i]] = getObjectKeys(obj[keys[i]]);
            }
        }
    }

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


blocks|key|1219484|text|使用ES6，您可以使用forEach遍历对象的键。要获取所有键，可以使用Object.keys，它返回对象中的所有键|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1219485|Object.keys(obj).forEach(function(keyValue,+index,+map)+{+
++console.log(keyValue);+
});|code-block|syntax|javascript|1219486|上面的代码片段的简写是，它只接受一个参数|1219487|Object.keys(obj).forEach(function(keyValue)+{+
++console.log(keyValue);+
});|1219488|entityMap^0|B|7|10|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

<p>Using ES6, 
you can use <code>forEach</code> to iterate over the Keys of an Object.
To get all the keys you can use <code>Object.keys</code> which returns all the keys in an Object</p>

<pre><code>Object.keys(obj).forEach(function(keyValue, index, map) { 
  console.log(keyValue); 
});
</code></pre>

<p>Short hand of the above snippet would be, which only takes one parameter</p>

<pre><code>Object.keys(obj).forEach(function(keyValue) { 
  console.log(keyValue); 
});
</code></pre>


blocks|key|1219495|text|var+obj+=+{
+++key1:+'value1',
+++key2:+'value2',
+++key3:+'value3',
+++key4:+'value4'
}

console.log(Object.keys(obj));
console.log(Object.keys(obj).length)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1219496|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 obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
}

console.log(Object.keys(obj));
console.log(Object.keys(obj).length)
</code></pre>


blocks|key|1219555|text|使用Object.keys()...这就是我们要做的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1219556|以下链接的MDN站点上提供了完整的文档：|1219557|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys|1219558|entityMap|0|LINK|mutability|MUTABLE|url^0|2|D|0|0|0|2K|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|U|8|@]|D|@$9|V|A|W|1|X]]|E|$]]|$1|J|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|I]]]]

<p>Use <code>Object.keys()</code>... it's the way to go.</p>

<p>Full documentation is available on the MDN site linked below:</p>

<p><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys" rel="nofollow noreferrer">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys</a></p>


blocks|key|1005187|text|如果你决定使用Underscore.js，你最好这样做|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1005188|var+obj+=+{
++++key1:+'value1',
++++key2:+'value2',
++++key3:+'value3',
++++key4:+'value4'
}

var+keys+=+[];
_.each(+obj,+function(+val,+key+)+{
++++keys.push(key);
});
console.log(keys.lenth,+keys);|code-block|syntax|javascript|1005189|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>If you decide to use Underscore.js you better do</p>

<pre class="lang-js prettyprint-override"><code>var obj = {
    key1: 'value1',
    key2: 'value2',
    key3: 'value3',
    key4: 'value4'
}

var keys = [];
_.each( obj, function( val, key ) {
    keys.push(key);
});
console.log(keys.lenth, keys);
</code></pre>


blocks|key|1005200|text|+++++++if(props.userType){
++++++++++var+data+=+[]
++++++++++Object.keys(props.userType).map(i=>{
++++++++++++++++data.push(props.userType[i])
++++++++++})
++++++++++setService(data)
++++++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1005201|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>       if(props.userType){
          var data = []
          Object.keys(props.userType).map(i=&gt;{
                data.push(props.userType[i])
          })
          setService(data)
        }
</code></pre>


blocks|key|1219618|text|现代浏览器确实支持：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1219619|​|1219620|var+obj+=+{
+++key1:+'value1',
+++key2:+'value2',
+++key3:+'value3',
+++key4:+'value4'
}
console.log(Object.keys(obj));
//+we+can+also+get+values
console.log(Object.values(obj));|code-block|syntax|javascript|1219621|1219622|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|N|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|K|$]]

<p>Modern browsers do support:</p>
<p><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 obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
}
console.log(Object.keys(obj));
// we can also get values
console.log(Object.values(obj));</code></pre>
</div>
</div>
</p>


<p>I have a JavaScript object like</p>

<pre><code>var obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
}
</code></pre>

<p>How can I get the length and list of keys in this object?</p>


Getting JavaScript object key list

JSON

我有一个JavaScript对象，比如var obj = {   key1: 'value1',   key2: 'value2',   key3: 'value3',   key4: 'value4'}如何获取此对象中键的长度和列表？

问获取JavaScript对象键列表
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