function getKeyByValue(object, value) {
  return Object.keys(object).find(key => object[key] === value);
}

ES6，没有原型突变或外部库。

的例子,

函数getKeyByValue(对象，值){ 返回种(对象)。Find (key =>对象[key] === value); ｝ Const map = {"first": "1"， "second": "2"}; console.log (getKeyByValue(地图,“2”));

lodash way https://lodash.com/docs#findKey

Var用户= { 'barney':{'年龄':36，'活跃':true}， 'fred': {'age': 40， 'active': false}， '鹅卵石':{'年龄':1，'活动':true} }; _。findKey(users， {'age': 1， 'active': true}); //→'鹅卵石'

如前所述，迭代是必要的。例如，在现代浏览器中，你可以有:

var key = Object.keys(obj).filter(function(key) {return obj[key] === value})[0];

value包含了你要找的值。 说到这里，我可能会使用循环。

否则，你可以使用一个合适的“hashmap”对象——在JS中有几个实现——或者你自己实现。

更新2018

六年过去了，但我仍然得到了一些投票，所以我觉得一个更现代的解决方案——适用于现代浏览器/环境——应该在答案中提到，而不仅仅是在评论中:

const key = Object.keys(obj).find(key => obj[key] === value);

当然它也可以是一个函数:

const getKeyByValue = (obj, value) => 
        Object.keys(obj).find(key => obj[key] === value);

这里有一个Lodash解决方案，适用于flat key =>值对象，而不是嵌套对象。已接受的答案建议使用_。findKey适用于具有嵌套对象的对象，但在这种常见情况下不起作用。

这种方法将对象颠倒，将键交换为值，然后通过查找新(颠倒的)对象上的值来查找键。如果没有找到键，则返回false，我更喜欢undefined，但你可以很容易地在_的第三个参数中交换它。getKey()中的get方法。

// Get an object's key by value var getKey = function( obj, value ) { var inverse = _.invert( obj ); return _.get( inverse, value, false ); }; // US states used as an example var states = { "AL": "Alabama", "AK": "Alaska", "AS": "American Samoa", "AZ": "Arizona", "AR": "Arkansas", "CA": "California", "CO": "Colorado", "CT": "Connecticut", "DE": "Delaware", "DC": "District Of Columbia", "FM": "Federated States Of Micronesia", "FL": "Florida", "GA": "Georgia", "GU": "Guam", "HI": "Hawaii", "ID": "Idaho", "IL": "Illinois", "IN": "Indiana", "IA": "Iowa", "KS": "Kansas", "KY": "Kentucky", "LA": "Louisiana", "ME": "Maine", "MH": "Marshall Islands", "MD": "Maryland", "MA": "Massachusetts", "MI": "Michigan", "MN": "Minnesota", "MS": "Mississippi", "MO": "Missouri", "MT": "Montana", "NE": "Nebraska", "NV": "Nevada", "NH": "New Hampshire", "NJ": "New Jersey", "NM": "New Mexico", "NY": "New York", "NC": "North Carolina", "ND": "North Dakota", "MP": "Northern Mariana Islands", "OH": "Ohio", "OK": "Oklahoma", "OR": "Oregon", "PW": "Palau", "PA": "Pennsylvania", "PR": "Puerto Rico", "RI": "Rhode Island", "SC": "South Carolina", "SD": "South Dakota", "TN": "Tennessee", "TX": "Texas", "UT": "Utah", "VT": "Vermont", "VI": "Virgin Islands", "VA": "Virginia", "WA": "Washington", "WV": "West Virginia", "WI": "Wisconsin", "WY": "Wyoming" }; console.log( 'The key for "Massachusetts" is "' + getKey( states, 'Massachusetts' ) + '"' ); <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

保持原型干净。

function val2key(val,array){
    for (var key in array) {
        if(array[key] == val){
            return key;
        }
    }
 return false;
}

例子:

var map = {"first" : 1, "second" : 2};
var key = val2key(2,map); /*returns "second"*/

真的很简单。

const CryptoEnum = Object.freeze({
                    "Bitcoin": 0, "Ethereum": 1, 
                    "Filecoin": 2, "Monero": 3, 
                    "EOS": 4, "Cardano": 5, 
                    "NEO": 6, "Dash": 7, 
                    "Zcash": 8, "Decred": 9 
                  });

Object.entries(CryptoEnum)[0][0]
// output => "Bitcoin"