我有一个非常简单的JavaScript对象，我将其用作关联数组。是否有一个简单的函数允许我获取值的键，或者我必须迭代对象并手动找到它?
当前回答
如果你正在使用下划线或Lodash库，你可以使用_。findKey功能:
var users = {
'barney': { 'age': 36, 'active': true },
'fred': { 'age': 40, 'active': false },
'pebbles': { 'age': 1, 'active': true }
};
_.findKey(users, function(o) { return o.age < 40; });
// => 'barney' (iteration order is not guaranteed)
// The `_.matches` iteratee shorthand.
_.findKey(users, { 'age': 1, 'active': true });
// => 'pebbles'
// The `_.matchesProperty` iteratee shorthand.
_.findKey(users, ['active', false]);
// => 'fred'
// The `_.property` iteratee shorthand.
_.findKey(users, 'active');
// => 'barney'
其他回答
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'
我们可以使用简单的函数来获取传递的值
const getKeyByValue = (object, value) => Object.keys(object).find(key => object[key] === value)
使用Underscore.js库:
var hash = {
foo: 1,
bar: 2
};
(_.invert(hash))[1]; // => 'foo'
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>
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”));
