Array.prototype without modifying original array

Question

I want to create a new Array method without modifying the original array.

my_array.push('foo') //modifies my_array
my_array.slice(2) //returns a new array without modifying my_array

I'd like to make a new Array.prototype method that returns an array without modifying the array it was called upon. So this would be possible:

//[define new method here] Array.prototype.add_foo = function() {...
var my_array = ['poo'];

my_array.add_foo(); //would return ['poo', 'foo'];
my_array; //would return ['poo'];

Okay, create a new array and return it instead of modifying this — Paul
– Paul, Commented Aug 29, 2014 at 2:45

Nathan Tuggy · Accepted Answer · 2017-06-24 06:47:04Z

10

my_array.concat('foo');

concat doesn't alter the original array.

edited Jun 24, 2017 at 6:47

Nathan Tuggy

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answered Jun 24, 2017 at 6:25

benjaminadk

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Comments

spender · Accepted Answer · 2014-08-29 02:47:00Z

2

Array.prototype.add_foo = function(){
    var ret = this.slice(0); //make a clone
    ret.push("foo"); //add the foo
    return ret; //return the modified clone
}

answered Aug 29, 2014 at 2:47

spender

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3 Comments

elclanrs Over a year ago

Simpler: return this.concat('foo')

spender Over a year ago

@elclanrs : Good. I've never used/spotted .concat. Thx

northamerican Over a year ago

For some reason I had the impression I could only return a modified version of the original array and not a new instance of Array. thanks

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