Spread vs Rest operator in JavaScript ES6

Rest and spread operators may appear similar in notation, but they serve distinct purposes in JavaScript, which can sometimes lead to confusion. Let’s delve into their differences and how each is used. Rest and spread operators are both introduced in javascript ES6.

Rest Operator

The rest operator is represented by three dots (…). When used in a function’s parameter list, it catches any extra arguments passed to the function and packs them neatly into an array. This allows functions to handle varying numbers of arguments without explicitly defining them. So, you can think of it as a way to gather up the remaining arguments into an array for easy handling inside the function.

Example: The rest operator gathers all arguments passed to the function after the first one (10 in this case) into an array called rest.

Javascript

function abc(a, ...rest) {
return rest;
}
console.log(abc(10, 1, 2, 3, 4, 5));

Output

[ 1, 2, 3, 4, 5 ]

Spread Operator

The spread operator, represented by three dots (…), works by taking all the items in an array and spreading them out, essentially unpacking the array so that each item becomes an individual element. It’s like taking a bunch of items from a box and laying them out separately on a table. This makes it easier to work with the individual items rather than dealing with the entire array as a single entity.

Example: This example shows the use of SPread Operator

Javascript

function abc(a, b, c) {
return a + b + c;
}

console.log(abc(...[1, 2, 3]));

Output

6

DIfference between Spread Operator and Rest Operator

Feature	Spread Operator	Rest Operator
Syntax	Denoted by three consecutive dots (…)	Denoted by three consecutive dots (…)
Usage	Used to expand an iterable into individual elements	Used in function parameters to gather arguments
Example	[…array]	function functionName(…args) { … }
Parameter Position	Can be used anywhere in an array literal or function call	Must be the last parameter in a function’s parameter list
Return Value	Creates a new array with copied elements Note: See the above explanation	Gathers remaining arguments into an array Note: See the above explanation
Mutability	Does not modify the original array or object Note: See the above explanation	Gathers arguments into an array without altering them Note: See the above explanation
Use Cases	Concatenating arrays, passing arrays as arguments	Capturing an arbitrary number of function arguments