Spread operator

As the name suggests the spread operator spreads or expands an iterable such as an array or string into individual elements.

Few use cases

• Adding elements of one array to new array.
• Passing an array as argument to a function.
• Array concatenation.
• Array copy.

Adding elements of one array to new array

var arr1 = [3,4,5];
var arr2 = [1,2,...arr1,6,7];
console.log(arr2); // output -> [1,2,3,4,5,6,7]

Passing an array as argument to a function

function addAll(a,b,c,d){
console.log(a+b+c+d); // output -> 10
}
var arr = [1,2,3,4];
addAll(...arr);

Array concatenation

var arr1 = [1,2,3];
var arr2 = [4,5,6];
arr1 = [...arr1,...arr2];
console.log(arr1); // output -> [1,2,3,4,5,6]

Array copy

var arr1 = [1,2,3,4];
var arr2 = [...arr1];
console.log(arr2); // output -> [1,2,3,4]

Rest parameters

The rest parameter syntax allows us to represent an indefinite number of arguments as an array.

function findProduct(...args){
var result = 1;
args.map((arg)=>{
result = result * arg;
});
return result;
}

console.log(findProduct(2,4,6)); // output -> 48

Points to take away

• Spread operator unpacks an iterable into individual elements.
• Rest parameter collects multiple individual elements and packs them into an array.