My Notes on Javascript

Arguments Object

You can pass more arguments to a function than it accepts.

function sample(one) { 
 console.log(one); // firstarg
 console.log(arguments); // Arguments(4) ["firstarg", 2, true, "sugar", callee: f, Symbol(Symbol.iterator): f]
}

sample('firstarg', 2, true, 'sugar');

Like an Array, arguments can be accessed by an index and has a length.

 arguments[0] // firstarg
 arguments[1] // 2
 arguments[2] // true
 arguments.length // 4

Arguments is an Object, Not an Array

Arguments can not use array methods, like pop() and push(). Different ways to put arguments object into an array:

  var args = [].slice.call(arguments); 
  var args = [].slice.call(arguments, 1); // start copying elements from index 1
  var args = [...arguments];  // ES6 
  var args = Array.from(arguments); // ES6
  // note Array.from(arguments, 1); is invalid

For more info:

Arguments Object

Array.from()

Example Use.

Pass an array, followed by one or more arguments to the destroy function.

destroy([1, 2, 3, 1, 2, 3], 2, 3);

Task: Remove all elements from the initial array that are of the same value as these arguments. In the example, removing 2 and 3 from the array [1, 2, 3, 1, 2, 3] will result in [1, 1]

function destroy(arr) {  
 var destroyNums = [].slice.call(arguments, 1); // [2, 3]
 
 // keep val if decision is true
 var arr2 = arr.filter(function(val) {
     var decision = false;
     // if array destroyNums does not have val, indexOf will return -1
     if (destroyNums.indexOf(val) === -1) {
       decision = true;
     }
     return decision;   
 }); 
 
 console.log("the final array: " + arr2) ; // the final array: 1, 1
 return arr2;  
}

The challenge is from freecodecamp, and the solution is my own