Parameter Handling.md

Parameter Handling

In ES6, handling a parameter has become lot easier.

Table of Contents

1. Default Parameter
2. Resting Parameter
3. Spread Parameter

Default Parameter

Demo

Your can passing a default parameter in function argument.

function funz(a, b = 5) {
	console.log(a + b); //print 6
}

// Equivalent to: b === 5 if b is undefined or not passed
funz(1);

Converted as

function funz(a) {
	var b = arguments.length <= 1 || arguments[1] === undefined ? 5 : arguments[1];

	console.log(a + b); //print 6
}

// Equivalent to: b === 5 if b is undefined or not passed
funz(1);

From now on, converted venilla js code will not be added, Check the output in the demo link.

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Resting Parameter

Demo

Passing a ... resting parameter at end of the function argument means that last argument will be received as an array.

function funz(a, ...b) {
	console.log(a, b); //print 1 [2, 3, 4]
}

funz(1, 2, 3, 4); // a = 1; b = [2, 3, 4]

Spread Parameter

Demo

Passing a ... spread parameter in function argument means that passing each element of array as argument.

function funz(a, b, c, d) {
	console.log(a); //print 1
	console.log(b); //print 2
	console.log(c); //print 3
	console.log(d); //print 4
}

funz(...[1, 2, 3, 4]);

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Reference

• Rest Spread