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Usage of rest parameter and spread operator in JavaScript?
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>
function addition(…numbers) {
var res = 0;
numbers.forEach(function (number) {
res += number;
});
return res;
}
document.write(addition(3));
document.write(addition(9,10,11,12,13));
</script>
</body>
</html>Spread Operator
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
<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);
// spread operator
f = [...a, b, ...c, d];
document.write(e);
document.write("<br>"+f);
</script>
</body>
</html>
Updated on: 16-Jun-2020
215 Views
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