rest operator code example

Example 1: the rest operator javascript

function sum(...numbers) {
	return numbers.reduce((accumulator, current) => {
		return accumulator += current;
	});
};
 
sum(1,2) // 3
sum(1,2,3,4,5) // 15

Example 2: rest parameter javascript

function addition(...nombre) {

    let resultat = 0
    
    nombre.forEach(nombre => {
       resultat+= nombre ;
    }); 

    console.log(resultat) ;
    
}

addition(4 ,9 ,5 ,415 ,78 , 54) ;

Example 3: rest parameters

// Before rest parameters, "arguments" could be converted to a normal array using:

function f(a, b) {

  let normalArray = Array.prototype.slice.call(arguments)
  // -- or --
  let normalArray = [].slice.call(arguments)
  // -- or --
  let normalArray = Array.from(arguments)

  let first = normalArray.shift()  // OK, gives the first argument
  let first = arguments.shift()    // ERROR (arguments is not a normal array)
}

// Now, you can easily gain access to a normal array using a rest parameter

function f(...args) {
  let normalArray = args
  let first = normalArray.shift() // OK, gives the first argument
}

Example 4: how to assign an rest operator in javascript

function multiply(multiplier, ...theArgs) {
  return theArgs.map(element => {
    return multiplier * element
  })
}

let arr = multiply(2, 1, 2, 3)
console.log(arr)  // [2, 4, 6]

Example 5: rest operator javascript

function fun1(...theArgs) {
  console.log(theArgs.length);
}

fun1();  // 0
fun1(5); // 1
fun1(5, 6, 7); // 3