Usage of rest parameter and spread operator in JavaScript?

JavascriptWeb DevelopmentFront End Technology

Rest Parameter

With rest parameter, you can represent a number of arguments as an array. ES6 brought rest parameter to ease the work of developers. For arguments objects, rest parameters are indicated by three dots … and precedes a parameter.

Let’s see the following code snippet to define rest parameter −

<html>
<body>
<script>
var res = 0;
numbers.forEach(function (number) {
res += number;
});
return res;
}
</script>
</body>
</html>

The spread operator will allow you to split an array into single arguments. These arguments are those, which are the functions as separate arguments.

Syntax

Here’s the syntax −

function myfunction(...iterableObj);

Here’s an example showing Spread Syntax with arguments:

function multiply(x, y) {
return x*y;
}
var myArgs = [50, 100]; console.log(multiply(…myArgs));

Example

Here’s another example

Live demo

<html>
<body>
<script>
var a, b, c, d, e, f, g;
a = [10,20];
b = "rank";
c = [30, "points"];
d = "run"

// concat method.
e = a.concat(b, c, d);

</html>