"Undefined" in javascript: Amazing Cases.

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In JavaScript, "undefined" is a primitive data type that represents a value that is not assigned to a variable or a property. "undefined" is a property of theglobal object. That is, it is a variable in global scope.

JavaScript uses theundefinedvalue in the following situations.

1)
When we declare avariableand dont initialize it to a value, the variable will have a value of''undefined''.
For example:

let x;console.log(x); // Output: undefined

2) -
If we access a non-existingproperty of an object, well getundefined.
For example:

let person = {name: "Sachin",};console.log(person.age); // undefined

In this example, theperson object has one property"name". Accessing the"age" property that doesnt exist on the"person" object returnsundefined.

3)
when we call thefunction and dont pass all the arguments, the parameters inside the function becomeundefined.
For example:

const calculation = (a, b ) => {return b === 7 ? ${ a } : ${ a} ${ b };}calculation(3); // 3 undefined

4)
A function that doesnt have areturnstatement implicitly returnsundefined.
For example:

function myFunc() {// Do something but don't return a value}console.log(myFunc()); // Output: undefined

5) --
When we access anarrayelement that is out-of-bounds, we'll get theundefinedvalue.
For example:

const colors = ['red', 'green', 'blue'];console.log(colors[3]); // undefined`

Theundefinedis a primitive type that has a single valueundefined.
Accessing an uninitialized variable returnsundefined.
Accessing a non-existing property of an object returnsundefined.
Accessing an out-of-bounds array element returnsundefined.
A function without areturnstatement or with areturnstatement but without an expression returnsundefined.

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