Remove array of indexes from array

Question

John Resig, creator of jQuery created a very handy Array.remove method that I always use it in my projects:

// Array Remove - By John Resig (MIT Licensed)
Array.prototype.remove = function(from, to) {
  var rest = this.slice((to || from) + 1 || this.length);
  this.length = from < 0 ? this.length + from : from;
  return this.push.apply(this, rest);
};

// Remove the second item from the array
array.remove(1);
// Remove the second-to-last item from the array
array.remove(-2);
// Remove the second and third items from the array
array.remove(1,2);
// Remove the last and second-to-last items from the array
array.remove(-2,-1);

It works great. But I would like to know if it's extendable so that it can take an array of indexes as the first argument?

Otherwise, I will probably make another method that makes use of it:

if (!Array.prototype.removeIndexes) {

    Array.prototype.removeIndexes = function (indexes) {

        var arr = this;

        if (!jQuery)
            throw new ReferenceError('jQuery not loaded');

        $.each(indexes, function (k, v) {

            var index = $.inArray(v, indexes);

            if (index !== -1)
                arr.remove(index);

        });
    };
}

If Array.remove() isn't extendable to fit my needs, what do you think about my other solution above?

Don’t modify objects you don’t own - even if J. Resig does so — tmaximini
– tmaximini, Commented Jun 25, 2013 at 9:00

score 1 · Accepted Answer · 2013-06-25 12:34:02Z

1

This version should work. It modifies the original array. If you prefer to return a new array without modifying the original, use the commented out initializer of result and add return result at the end of the function.

Array.prototype.removeIndexes = function(indices) { 
  // make sure to remove the largest index first
  indices = indices.sort(function(l, r) { return r - l; });

  // copy the original so it is not changed
  // var result = Array.prototype.slice.call(this);

  // modify the original array
  var result = this;

  $.each(indices, function(k, ix) {
    result.splice(ix, 1);
  });
}

> [0, 1, 2, 3, 4, 5, 6, 7, 8].removeIndexes([4, 5, 1]);
> [0, 2, 3, 6, 7, 8]

edited Jun 25, 2013 at 12:34

answered Jun 25, 2013 at 8:24

user1233508

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4 Comments

user1233508 Over a year ago

@Johan: this function returns a new array without modifying the original.

Johan Over a year ago

Ok, can it be adjusted so that it modifies the actual array that you're using it on?

Johan Over a year ago

Thank you. How would splice() handle a -1-index?

Damien Over a year ago

It doesn't. ['a', 'b', 'c', 'd', 'e', 'f'].removeIndexes([-1,-3]); returns : [a, b, d, e ] instead of [a, b, c, e ]

Damien · Accepted Answer · 2013-06-25 12:25:46Z

1

I think this is what you are looking for (It works with negative index too) :

if (!Array.prototype.removeIndexes) {

    Array.prototype.removeIndexes = function (indexes) {

        var arr = this;

        if (!jQuery) throw new ReferenceError('jQuery not loaded');

        var offset = 0;

        for (var i = 0; i < indexes.length - 1; i++) {
            if (indexes[i] < 0)
                indexes[i] = arr.length + indexes[i];
            if (indexes[i] < 0 || indexes[i] >= arr.length)
                throw new Error('Index out of range');
        }

        indexes = indexes.sort();

        for (var i = 0; i < indexes.length - 1; i++) {
            if (indexes[i + 1] == indexes[i])
                throw new Error('Duplicated indexes');
        }


        $.each(indexes, function (k, index) {
            arr.splice(index - offset, 1);
            offset++;
        });
        return arr;
    };
}

var a = ['a', 'b', 'c', 'd', 'e', 'f'];
var ind = [3, 2, 4];

a.removeIndexes(ind);

console.log(a.join(', '));
// returns : a, b, f

See fiddle

edited Jun 25, 2013 at 12:25

answered Jun 25, 2013 at 8:37

Damien

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3 Comments

Johan Over a year ago

Thanks. WHat will happen if I pass an index that doesn't exist? Like -1

Damien Over a year ago

If you pass a wrong index an error will be throw. You can use negative numbers to select from the end of an array (as the splice function).

Johan Over a year ago

Btw, there index is undefined in indexes[i] = arr.length + index;. Did you mean indexes[i] = arr.length + indexes[i];?

Atif · Accepted Answer · 2013-06-25 08:19:26Z

0

How about

Array.prototype.remove = function (indexes) {
    if(indexes.prototype.constructor.name == "Array") {
        // your code to support indexes
    } else {
        // the regular code to remove single or multiple indexes
    }

};

answered Jun 25, 2013 at 8:19

Atif

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