如何使用 JavaScript 检查对象中是否存在值

Question

I have an object in JavaScript:

var obj = {
   "a": "test1",
   "b": "test2"
}

How do I check that test1 exists in the object as a value?

Answer 1

You can turn the values of an Object into an array and test that a string is present. It assumes that the Object is not nested and the string is an exact match:

var obj = { a: 'test1', b: 'test2' };
if (Object.values(obj).indexOf('test1') > -1) {
   console.log('has test1');
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values

Answer 2

最短的 ES6+ 一个班轮：

let exists = Object.values(obj).includes("test1");

Answer 3

You can use the Array method .some :

var exists = Object.keys(obj).some(function(k) {
    return obj[k] === "test1";
});

Answer 4

Try:

 var obj = { "a": "test1", "b": "test2" }; Object.keys(obj).forEach(function(key) { if (obj[key] == 'test1') { alert('exists'); } });

Or

 var obj = { "a": "test1", "b": "test2" }; var found = Object.keys(obj).filter(function(key) { return obj[key] === 'test1'; }); if (found.length) { alert('exists'); }

This will not work for NaN and -0 for those values. You can use (instead of === ) what is new in ECMAScript 6:

 Object.is(obj[key], value);

With modern browsers you can also use:

 var obj = { "a": "test1", "b": "test2" }; if (Object.values(obj).includes('test1')) { alert('exists'); }

Answer 5

Use a for...in loop:

for (let k in obj) {
    if (obj[k] === "test1") {
        return true;
    }
}

Answer 6

You can use Object.values() :

The Object.values() method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).

and then use the indexOf() method:

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

For example:

Object.values(obj).indexOf("test`") >= 0

A more verbose example is below:

 var obj = { "a": "test1", "b": "test2" } console.log(Object.values(obj).indexOf("test1")); // 0 console.log(Object.values(obj).indexOf("test2")); // 1 console.log(Object.values(obj).indexOf("test1") >= 0); // true console.log(Object.values(obj).indexOf("test2") >= 0); // true console.log(Object.values(obj).indexOf("test10")); // -1 console.log(Object.values(obj).indexOf("test10") >= 0); // false

Answer 7

For a one-liner, I would say:

exist = Object.values(obj).includes("test1");
console.log(exist);

Answer 8

I did a test with all these examples, and I ran this in Node.js v8.11.2 . Take this as a guide to select your best choice.

 let i, tt; const obj = { a: 'test1', b: 'test2', c: 'test3', d: 'test4', e: 'test5', f: 'test6' }; console.time("test1") i = 0; for( ; i<1000000; i=i+1) { if (Object.values(obj).indexOf('test4') > -1) { tt = true; } } console.timeEnd("test1") console.time("test1.1") i = 0; for( ; i<1000000 ; i=i+1) { if (~Object.values(obj).indexOf('test4')) { tt = true; } } console.timeEnd("test1.1") console.time("test2") i = 0; for( ; i<1000000; i=i+1) { if (Object.values(obj).includes('test4')) { tt = true; } } console.timeEnd("test2") console.time("test3") i = 0; for( ; i<1000000 ; i=i+1) { for(const item in obj) { if(obj[item] == 'test4') { tt = true; break; } } } console.timeEnd("test3") console.time("test3.1") i = 0; for( ; i<1000000; i=i+1) { for(const [item, value] in obj) { if(value == 'test4') { tt = true; break; } } } console.timeEnd("test3.1") console.time("test4") i = 0; for( ; i<1000000; i=i+1) { tt = Object.values(obj).some((val, val2) => { return val == "test4" }); } console.timeEnd("test4") console.time("test5") i = 0; for( ; i<1000000; i=i+1) { const arr = Object.keys(obj); const len = arr.length; let i2 = 0; for( ; i2<len ; i2=i2+1) { if(obj[arr[i2]] == "test4") { tt = true; break; } } } console.timeEnd("test5")

Output on my server

test1:   272.325 ms
test1.1: 246.316 ms
test2:   251.98 0ms
test3:    73.284 ms
test3.1: 102.029 ms
test4:   339.299 ms
test5:    85.527 ms

Answer 9

if (Object.values(obj).includes('test1')){
   return true
}

Answer 10

you can try this one

var obj = {
  "a": "test1",
  "b": "test2"
};

const findSpecificStr = (obj, str) => {
  return Object.values(obj).includes(str);
}

findSpecificStr(obj, 'test1');

Answer 11

You can try this:

function checkIfExistingValue(obj, key, value) {
    return obj.hasOwnProperty(key) && obj[key] === value;
}
var test = [{name : "jack", sex: F}, {name: "joe", sex: M}]
console.log(test.some(function(person) { return checkIfExistingValue(person, "name", "jack"); }));

Answer 12

In new version if ecma script now we can check vslues by ?. operations..

Its so simpler and easy yo check values in a object or nested or objects

var obj = {
   "a": "test1",
   "b": "test2"
}

if(obj?.a) return "i got the value"

Similarly since in Javascript most used primitive type is Object

We can use this arrays, functions etc too

aFunc = () => { return "gotcha"; }

aFunc?.() // returns gotcha

myArray = [1,2,3]

myArray?.[3] // returns undefined

Thanks

Answer 13

Best way to find value exists in an Object using Object.keys()

obj = {
 "India" : {
 "Karnataka" : ["Bangalore", "Mysore"],
 "Maharashtra" : ["Mumbai", "Pune"]
 },
 "USA" : {
 "Texas" : ["Dallas", "Houston"],
 "IL" : ["Chicago", "Aurora", "Pune"]
 }
}

function nameCity(e){
    var finalAns = []
    var ans = [];
    ans = Object.keys(e).forEach((a)=>{
        for(var c in e[a]){
            e[a][c].forEach(v=>{
                if(v === "Pune"){
                    finalAns.push(c)
                }
            })

        }
    })
    console.log(finalAns)
}


nameCity(obj)

Answer 14

var obj = {"a": "test1", "b": "test2"};
var getValuesOfObject = Object.values(obj)
for(index = 0; index < getValuesOfObject.length; index++){
    return Boolean(getValuesOfObject[index] === "test1")
}

The Object.values() method returned an array (assigned to getValuesOfObject) containing the given object's (obj) own enumerable property values. The array was iterated using the for loop to retrieve each value (values in the getValuesfromObject) and returns a Boolean() function to find out if the expression ("text1" is a value in the looping array) is true.

Answer 15

getValue = function (object, key) {
    return key.split(".").reduce(function (obj, val) {
        return (typeof obj == "undefined" || obj === null || obj === "") ? obj : (_.isString(obj[val]) ? obj[val].trim() : obj[val]);}, object);
};

var obj = {
   "a": "test1",
   "b": "test2"
};

Function called:

 getValue(obj, "a");

Answer 16

For complex structures, here is how I do it:

 const obj = { test: [{t: 't'}, {t1: 't1'}, {t2: 't2'}], rest: [{r: 'r'}, {r1: 'r1'}, {r2: 'r2'}] } console.log(JSON.stringify(obj).includes(JSON.stringify({r1: 'r1'}))) // returns true console.log(JSON.stringify(obj).includes(JSON.stringify({r1: 'r2'}))) // returns false

Answer 17

_.has() method is used to check whether the path is a direct property of the object or not. It returns true if the path exists, else it returns false.

 var object = { 'a': { 'b': 2 } }; console.log(_.has(object, 'a.b')); console.log(_.has(object, ['a','b'])); console.log(_.has(object, ['a','b','c']));

Output: true true false

Answer 18

if( myObj.hasOwnProperty('key') && myObj['key'] === value ){
    ...
}

Answer 19

The simple answer to this is given below.

This is working because every JavaScript type has a “constructor” property on it prototype ”.

let array = []
array.constructor === Array
// => true


let data = {}
data.constructor === Object
// => true

Answer 20

This should be a simple check.

Example 1

var myObj = {"a": "test1"}

if(myObj.a == "test1") {
    alert("test1 exists!");
}