JavaScript Remove Multiple Values from Array Using Filter and Loop

Question

I'm new here and need some help with writing a function destroyer() to remove multiple values from an array.

The destroyer() function passes in an array and additional numbers as arguments. The idea is to remove the numbers from the array.

E.g.

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

Output: [1, 1]

destroyer(["tree", "hamburger", 53], "tree", 53)

Output: ["hamburger"]

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

Output: []

Note: the examples only show 2 additional numbers to remove. But the function destroyer() should be able to remove any number of values (i.e. 4, 5, or 6 parameters).

However, my code does not produce the same result. Specifically, using console.log, I see that my filterer function does not loop properly.

1) Can anyone help me debug?

2) Any better way to write this function?

Thank you very much!!!

function destroyer() {

  var args = Array.prototype.slice.call(arguments); 

  var itemToRemove = args.slice(1);
  console.log(itemToRemove);
  var newArr = args[0];
  console.log(newArr);

  function filterer(value) { 

    for (var i = 0; i < itemToRemove.length; i++) {
      console.log(i);
      console.log(itemToRemove[i]);
      if (value != itemToRemove[i]) {
        return value;
      }
    } 
   }

  return newArr.filter(filterer);
}

If you told us what the criteria was for removing, instead of posting cryptic examples, it would probably be easier to help ? — adeneo
– adeneo, Commented Oct 22, 2015 at 6:12
In the first argument he passes an array, in the further the values he wants to remove — h0ch5tr4355
– h0ch5tr4355, Commented Oct 22, 2015 at 6:14
Do you always pass two values for removing? or it can be more? like destroyer([1, 2, 3, 1, 2, 3], 2,4, 3)? — Grundy
– Grundy, Commented Oct 22, 2015 at 6:57
It can be any number of values, e.g. 3 values to remove in your example. — Neong
– Neong, Commented Oct 22, 2015 at 7:02

ykravv · Accepted Answer · 2015-10-22 06:25:14Z

4

Your filterer function can be much simpler:

function filterer (value) {
    return itemToRemove.indexOf(value) === -1;
}

answered Oct 22, 2015 at 6:25

ykravv

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1 Comment

Grundy Over a year ago

@Neong, note, it can be not fast on big array, with many items to remove

Shashank · Accepted Answer · 2015-10-22 09:02:12Z

0

Using Array.prototype.indexOf() can be inefficient compared to object property lookup in terms of time complexity. I would recommend looping through the additional arguments once and constructing an object with target elements to be destroyed as keys. Then you can check if a given value is a target or not within a filtering callback that you pass to Array.prototype.filter().

function destroyer() {
    var arr = arguments.length && arguments[0] || [];
    var targets = {};
    for (var i = 1; i < arguments.length; i++) {
        targets[arguments[i]] = true;
    }
    return arr.filter(function (x) {
        return targets[x] === undefined;
    });
}

One downside to this approach is that not all values in JS can be valid properties of an object, since properties must be strings. In this case, you're just using numbers as keys, and those numbers are implicitly converted to strings.

edited Oct 22, 2015 at 9:02

answered Oct 22, 2015 at 6:47

Shashank

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3 Comments

Grundy Over a year ago

i think in this case better targets[arguments[i]] = true or something like and in filter function targets[x] === undefiend. because hasOwnProperty is more complex function and slowest with comparing to undefined

Shashank Over a year ago

@Grundy Noted, I have edited the answer. Thank you for the suggestion.

Neong Over a year ago

Thank you Shashank and @Grundy for your help. It took me a while to understand this approach ;) Thank you for the perspective!

LeoTM · Accepted Answer · 2017-01-24 19:44:03Z

0

We can pass the arguments an extra parameter to our callback function in our filter() method.

function destroyer(arr) {
  return arr.filter(filterer(arguments)); // Pass arguments
}

function filterer(args) {
  return function(value) { // Actual filter function
    for (var i = 1; i < args.length; i++) {
      if (value === args[i]) // Seek
        return false; // Destroy
    }
    return true; // Otherwise keep
  };
}

This passes all 5 test cases for freeCodeCamp | Basic Algorithm Scripting | Seek and Destroy.

answered Jan 24, 2017 at 19:44

LeoTM

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Comments

Azad · Accepted Answer · 2015-10-22 06:44:22Z

-1

A simple function

function filter(arr, arg1, arg2){

    var j = arr.length;
    while(j){

       if (arr.indexOf(arg1) > -1 || arr.indexOf(arg2) > -1){
          arr.splice(j - 1, 1);
       }
       j--
    }
}

answered Oct 22, 2015 at 6:44

Azad

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6 Comments

Grundy Over a year ago

what if should be three additional params? or four? :-)

Azad Over a year ago

In his requirement needs two arguments, I wrote this function for that

Grundy Over a year ago

it just a sample, i think. also why you do two indexOf on every loop iteration, instead just testing array element and do splice if it equal arg1 or arg2?

Azad Over a year ago

I added another answer below

Neong Over a year ago

Sorry I wasn't clear but it can be any number of values to be removed -- 2, 3, 4, 5 etc.

|

Azad · Accepted Answer · 2015-10-22 09:10:53Z

-1

For multiple arguments

A simple function

function filter(){
    var j = -1; 
    for(var i = 1; i < arguments.length; i++){
        j = arguments[0].indexOf(arguments[i]);
        if(j > -1){
           arguments[0].splice(j, 1);
        }
    }
    return arguments[0];
}

you can call this function with no of args eg:

 filter([1,2,3,4,5,6,7,8,9], 1, 3, 5); //return [2,4,6,7,8,9]
 filter([1,2,3,4,5,6,7,8,9], 1); //return [2,3,4,5,6,7,8,9]

edited Oct 22, 2015 at 9:10

answered Oct 22, 2015 at 7:01

Azad

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11 Comments

Grundy Over a year ago

you not need in ...,arg1, arg2, arg3, arg4 and function filter(arr) is enough

Azad Over a year ago

Yes, #Grundy but this function should call with an array and arguments

Grundy Over a year ago

but now it seems like max args count is 4

Azad Over a year ago

It not depend on no of args

Grundy Over a year ago

i not say that it depends:-) i say - it seems like

|

MHernandez · Accepted Answer · 2016-10-01 02:34:47Z

-1

There are really good answers here, but you can do it very clean in this way, remember you have an objects option in filter method which you can use in the callback function, in this case i'm using it like : arguments[i] so I can check every value in the arguments array

function destroyer(arr) {

   for(var i = 1; i < arguments.length; i++){
     arr = arr.filter(isIn, arguments[i]);
   } 

   function isIn(element,index, array){
      if (element != this){
         return element;
      }
   }  
   return arr;
}

answered Oct 1, 2016 at 2:34

MHernandez

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