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I need to determine if a certain key exists in an array of objects.

Here is a sample array:

arrOfObj = [{
        "mainKey1": {
            "subKey1": {
                "innerKey1": {
                    "innerMostKey1": {
                        "key1": "value"
                    }
                }
            }
        }
    }, {
        "mainKey2": {
            "key2": "value"
        }
    }, {
        "mainKey3": {
            "subKey3": {
                "key3": "value"
            }
        }
    }
]

I was trying to do this but I get the wrong output:

const objKeys = Object.keys(arrOfObj)
console.log('objKeys = ' + JSON.stringify(arrOfObj))

Output is the index numbers:

objKeys = ["0", "1", "2"]

I want to have a function that works like this:

var isKeyPresent = checkKeyPresenceInArray('mainKey3')

Please note though that I only need to check the topmost level in the objects - in above example, these are the main keys (mainKey1, etc) and that their content is dynamic (some others have deeply nested object inside and some not so.

Help!

I need to determine if a certain key exists in an array of objects.

Here is a sample array:

arrOfObj = [{
        "mainKey1": {
            "subKey1": {
                "innerKey1": {
                    "innerMostKey1": {
                        "key1": "value"
                    }
                }
            }
        }
    }, {
        "mainKey2": {
            "key2": "value"
        }
    }, {
        "mainKey3": {
            "subKey3": {
                "key3": "value"
            }
        }
    }
]

I was trying to do this but I get the wrong output:

const objKeys = Object.keys(arrOfObj)
console.log('objKeys = ' + JSON.stringify(arrOfObj))

Output is the index numbers:

objKeys = ["0", "1", "2"]

I want to have a function that works like this:

var isKeyPresent = checkKeyPresenceInArray('mainKey3')

Please note though that I only need to check the topmost level in the objects - in above example, these are the main keys (mainKey1, etc) and that their content is dynamic (some others have deeply nested object inside and some not so.

Help!

• javascript
• arrays
• node.js
• json
• object

Share Improve this question Follow asked Apr 28, 2020 at 2:00 kzaiwokzaiwo 1,74833 gold badges2121 silver badges6262 bronze badges 3

• You need to find key of individual object, not the complete array, loop over the array using some array method and the for each individual element get the keys and test it against your desired key – Code Maniac Commented Apr 28, 2020 at 2:04
• Do you want to extract all keys in an array ? – Ala Eddine Menai Commented May 1, 2020 at 21:15
• You get 0,1,2because you passed an array, not an object. – Ala Eddine Menai Commented May 1, 2020 at 21:25

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6 Answers 6

Sorted by: Reset to default 13

You can try using array.some():

let checkKeyPresenceInArray = key => arrOfObj.some(obj => Object.keys(obj).includes(key));

let arrOfObj = [{
        "mainKey1": {
            "subKey1": {
                "innerKey1": {
                    "innerMostKey1": {
                        "key1": "value"
                    }
                }
            }
        }
    }, {
        "mainKey2": {
            "key2": "value"
        }
    }, {
        "mainKey3": {
            "subKey3": {
                "key3": "value"
            }
        }
    }
]

let checkKeyPresenceInArray = key => arrOfObj.some(obj => Object.keys(obj).includes(key));


var isKeyPresent = checkKeyPresenceInArray('mainKey3')

console.log(isKeyPresent);

You can iterate through the array, check and see if any of the objects has the key that you are looking for, and return true if it does. If you don't find the key, then the for loop will complete and it will return false.

arrOfObj = [{
        "mainKey1": {
            "subKey1": {
                "innerKey1": {
                    "innerMostKey1": {
                        "key1": "value"
                    }
                }
            }
        }
    }, {
        "mainKey2": {
            "key2": "value"
        }
    }, {
        "mainKey3": {
            "subKey3": {
                "key3": "value"
            }
        }
    }
]

function arrayHasKey(arr, key) {
  for (const obj of arr) {
    if (key in obj) { return true; }
  }
  return false;
}

console.log(arrayHasKey(arrOfObj, "mainKey2"))
console.log(arrayHasKey(arrOfObj, "mainKey10"))

this will work,it returns boolean value:

arrOfObj.hasOwnProperty('mainKey3');

You can use some with hasOwnProperty like this :

let checkKeyPresenceInArray = (key) => arrOfObj.some((o) => o.hasOwnProperty(key));

You have to use hasOwnProperty method to check if the key is available in the objects in that array -

var c = 0;
arrOfObj.forEach(e => {
  if(e.hasOwnProperty("mainKey1")){
       c++;
   }
});
if(c > 0 && c == arrOfObj.length){
    console.log("The key is found in all the objects in the array.");
}
else if(c == 0){
    console.log("The key is not found in any objects in the array");
}
else{
     console.log("The key is  found in some objects in the array");
}

It is possibly to apply JSON.stringify() for that purpose:

let list = [{
        "data1": {
            "subKey1": {
                "innerKey1": {
                    "innerMostKey1": {
                        "key1": "value"
                    }
                }
            }
        }
    }, {
        "data2": {
            "key2": "value"
        }
    }, {
        "data3": {
            "subKey3": {
                "key3": "value"
            }
        }
    }
]

let checkIfInArray = key => list.some(obj => JSON.stringify(obj).indexOf(key) > -1);


var result = checkIfInArray('key2')

alert(result);

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