JavaScript Filter Matrices

Question

I do online JavaScript courses and am curious about one of the tasks:

We are equipped with an initial array (the first argument in the destroyer function), followed by one or more arguments. We must remove all elements from the original array that have the same meaning as these arguments.

Here is my solution, but it does not work:

 function destroyer(arr) {
   // Separating the array from the numbers, that are for filtering; 
   var filterArr = [];
   for (var i = 1; i < arguments.length; i++) {
     filterArr.push(arguments[i]);
   }

   // This is just to check if we got the right numbers
   console.log(filterArr);

   // Setting the parameters for the filter function
   function filterIt(value) {
       for (var j = 0; j < filterArr.length; j++) {
         if (value === filterArr[j]) {
           return false;
         }
       }
     }
     // Let check what has been done
   return arguments[0].filter(filterIt);
 }

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

Run codeHide result

I was able to find a solution, but for me it makes no sense, so I am posting this question; could you tell me why the following code works:

function destroyer(arr) {
  // Separating the array from the numbers, that are for filtering; 
  var filterArr = [];
  for (var i = 1; i < arguments.length; i++) {
    filterArr.push(arguments[i]);
  }

  // This is just to check if we got the right numbers
  console.log(filterArr);

  // Setting the parameters for the filter function
  function filterIt(value) {
      for (var j = 0; j < filterArr.length; j++) {
        if (value === filterArr[j]) {
          return false;
        }
        // This true boolean  is what makes the code to run and I can't                  // understand why. I'll highly appreciate your explanations.
      }
      return true;
    }
    // Let check what has been done
  return arguments[0].filter(filterIt);
}

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

Run codeHide result

Thanks for the heads!

Answer 1

The code does not work because you are not returning true.

Array.filter . true, . false, .

, undefined , undefined - false. , .

MDN,

filter() , , true.

Answer 2

filter . , . , true , false, .

: Filter-Array

, , , true false ( , ).

true ( undefined, false Javscript, .

: true JS false JS.

Answer 3

, , , filter().

. :
: , Rajesh

function destroyer(arr) {

  for (var i = 1, filterArr = []; i < arguments.length; i++) {
    filterArr.push(arguments[i]);
  }

  return arguments[0].filter(function(v) {
    return filterArr.indexOf(v)===-1
  });
}

var result = destroyer([1, 2, 3, 1, 2, 5, 3], 2, 3);
console.log(result);

Answer 4

, Array.prototype.reduce() :

ES6

var destroyer = (a,...f) => a.reduce((p,c) => f.includes(c) ? p : p.concat(c),[]);
console.log(destroyer([1, 2, 3, 1, 2, 3], 2, 3));

Hide result

ES5

function destroyer(a){
  var f = Array.prototype.slice.call(arguments,1);
  return a.reduce(function(p,c){
                    return f.indexOf(c) !== -1 ? p : p.concat(c);
                  },[]);
}
console.log(destroyer([1, 2, 3, 1, 2, 3], 2, 3));

Hide result

Answer 5

, , , true, .

.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter