How To Check If An Element Exists Or Not In JavaScript If Undefined?

An undefined variable or anything without a value will always return undefined in JavaScript. This is not the same as null, despite the fact that both imply an empty state.

You’ll typically assign a value to a variable after you declare it, but this is not always the case.

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When a variable is declared or initialized but no value is assigned to it, JavaScript automatically displays “undefined”. It looks like this:

Errors:

let myStr;
console.log(myStr); // undefined

let user = {
    name: "John Doe",
    age: 14
};
console.log(user.hobby); // undefined

let myArr = [12, 33, 44]; 
console.log(myArr[7]); // undefined

Solutions:

if(myStr === undefined){}
if(typeof myArr[7] === "undefined"){}
if(user.hobby === void 0){}
if(document.querySelector("#ID") != "undefined"){}

Note: The undefined is not a reserved keyword in JavaScript, and thus it is possible to declare a variable with the name undefined. So the correct way to test an undefined variable or property is using the typeof operator, like this: if(typeof myVar === 'undefined').

 x === undefined; // Throws a ReferenceError
 typeof x == 'undefined'; // true

Customization:

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Troubleshooting the Errors:

Do it with concentration and patience. Check your all steps again and all codes or scripts. If you find any error you can contact us anytime via comment or better via email, We are always here to help you.

Final Words:

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