How to check if a key exists in an object in javascript

Question

I have the following object literal:

{ 
  'key1': 
  { 
    id: 'rr323',
    d: undefined,
    x: 560,
    y: 150 
  },
  'key2': 
  { 
    id: 'rr231',
    d: undefined,
    x: 860,
    y: 90 
  } 
}

I want to implement an if statement such as below:

if(key DOES NOT exist in object){  
//perform certain function 
}

I tried the following:

var key = key1;
if(!(key in global_move_obj)){
 // function
}

But that always returns true value when it should return false.

`var key = key1` in your code should be `var key = 'key1'`, otherwise you're going to check if `undefined in global_move_obj`. — zzzzBov, Jun 27 '16 at 20:08

score 18 · Accepted Answer · edited Feb 18 '22 at 14:55

18

Use the hasOwnProperty call:

if (!obj.hasOwnProperty(key)) {

}

edited Feb 18 '22 at 14:55

DᴀʀᴛʜVᴀᴅᴇʀ

7,681
17
73
127

answered Jun 27 '16 at 20:00

tymeJV

103,943
14
161
157

score 2 · Answer 2 · answered Jun 27 '16 at 20:02

2

You can do it like:

var key = 'key1';
if (!('key1' in obj)) {
    ....
} 
// or
if (!(key in obj)) {

}

answered Jun 27 '16 at 20:02

fedeghe

1,243
13
22

How to check if a key exists in an object in javascript

2 Answers2