how to assign an rest operator in javascript

// es6 rest parameter 
function fun(...input){ 
    let sum = 0; 
    for(let i of input){ 
        sum+=i; 
    } 
    return sum; 
} 
console.log(fun(1,2)); //3 
console.log(fun(1,2,3)); //6 
console.log(fun(1,2,3,4,5)); //15                  

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

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

function addition(...nombre) {

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

    console.log(resultat) ;
    
}

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