How do I search for a key of object in javascript

0 votes
I am checking for undefinedness for whether a key exists. What if the key exists but the value is actually undefined?

var obj = { key: undefined }; obj["key"] != undefined // false, but the key exists!
Oct 14, 2020 in Java-Script by Rehan
• 120 points
946 views

Hello @ Rehan ,

For that you can use in operator which return boolean result help you to identify key is associate with object or not

Thanks for your acknowledgment but do you have any example for the same so that i can use it?

The following examples show some uses of the in operator.

// Arrays
let trees = ['redwood', 'bay', 'cedar', 'oak', 'maple']
0 in trees        // returns true
3 in trees        // returns true
6 in trees        // returns false
'bay' in trees    // returns false (you must specify the index number, not the value at that index)
Yes, it can be used for Identification of key associated with object but if there are multiple objects so how can i able to identify for each object dynamically...sure this won't work if there are thousands of objects any help for that would be appreciated?

1 answer to this question.

0 votes

Use hasOwnProperty(key)

for (let i = 0; i < array.length; i++) {
        let a = obj[i].hasOwnProperty(`${key}`);
        if(a){
            console.log(obj[i])
       }
    }

Hope it helps you!!

answered Oct 14, 2020 by Niroj
• 82,820 points
Thanks man...it worked you saved my life

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