How do I search for a key of object in javascript

Question

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!

Comments

Hello @ Rehan ,

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

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

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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)

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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?

Answer 1

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!!

Comments

Thanks man...it worked you saved my life