REST PARAMETERS AND THE SPREAD OPERATOR

It can be very useful for a function to accept any number of arguments. For example, Math.max computes the maximum of all arguments it is given

But how can we write such a function 

well

the answer is rest parameter

look at this code:

function max(...numbers) {

    let result = -Infinity;

    for (let number of numbers) {

        if (number > result) result = number;

    }

    return result;

}

console.log(max(4, 1, 9, -2));

// → 9

in the above example the number argument contains all the value as an array (i,e. [4,1,9,-2]) , and it is our rest parameter.

a rest parameter takes extra arguments and hold them in an array.And the triple dot(...)

sign is called our spread operator.

for example:

function restParameter( num1, num2, ...remainingArguments ){

    console.log(remainingArguments);

}

restParameter(1,4,8,2,4);   // -> [8,2,4]

restParameter(3,4,5,2,1);   // -> [5,2,1]

when such a function is called the rest parameter holds all the remaining values. but, in case there are other parameters before it, their values are not part of that array.

when as in max,it is the only parameter, it will hold all arguments.

You can also use a similar three-dot notation to call a function with an array of

arguments. The spread operator pass each elements as separate arguments to the function.

let numbers = [5, 1, 7];

console.log(max(...numbers));

// → 5 1 7

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