Compute Sum #vanillajs

sum.js

//if you want the old way: 
function sum(){
  var sum =0; 
  for(var i=0;i<arguments.length;i++){
     sum += arguments[i];
  }
   return sum;
}
sum(1,2); // returns 3
sum(1,2,3); // returns 6

sum2.js

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

function sum(...theArgs) {
  return theArgs.reduce((previous, current) => {
    return previous + current;
  });
  
  
console.log(sum(1, 2, 3));
// expected output: 6

console.log(sum(1, 2, 3, 4));
// expected output: 10 

sum3.js

//As a helper function - Returns the sum of all values in a given array.
const arrSum = arr => arr.reduce((a,b) => a + b, 0)
// arrSum([20, 10, 5, 10]) -> 45

//function above is identical to

arrSum = function(arr){
  return arr.reduce(function(a,b){
    return a + b
  }, 0);
}

//src: https://codeburst.io/javascript-arrays-finding-the-minimum-maximum-sum-average-values-f02f1b0ce332