Add Array#insert

[jwestbrook]

previous lighthouse ticket #356
by quamis

---

I needed to b able to insert values in the middle of an array and did not find this functionality in prototype..so here it is:)

//extend the array object to support indexed insertions 
Array.prototype.insert=function(element,where) {

var slice1=this.slice(0,where);
var slice2=this.slice(where);

return new Array.concat(slice1,element,slice2);

};

[jwestbrook]

Tobie Langel
September 24th, 2008 @ 11:18 AM

State changed from “new” to “invalid”
That's already possible with the native splice method.

[jwestbrook]

Joe Gornick
September 24th, 2008 @ 07:15 PM

Here's a helper method I use to insert values into an array:

Object.extend(Array.prototype, {
  insert: function(index) {
    this.length = (index > this.length) ? index : this.length;
    index = (index < 0) ? this.length : index;

    this.splice.apply(this, [index, 0].concat(Array.slice(arguments, 1)));
    return this;
  }
});

Examples:

var a1 = new Array(1, 2, 3, 4, 5);
a1.insert(0, 0); // -> [0, 1, 2, 3, 4, 5]
a1.insert(-1, 6); // -> [0, 1, 2, 3, 4, 5, 6]
a1.insert(10, 10); // -> [0, 1, 2, 3, 4, 5, 6, undefined, undefined, undefined, 10]

[jwestbrook]

Joe Gornick
September 24th, 2008 @ 07:18 PM

Forgot to mention the insert method can take multiple arguments to insert.
To continue with the above example:

a1.insert(11, 11, 12, 13, 14); // -> [0, 1, 2, 3, 4, 5, 6, undefined, undefined, undefined, 10, 11, 12, 13, 14]

[jwestbrook]

[@]jdalton
September 24th, 2008 @ 07:48 PM

@joe - Very cool stuff :D.
Here are a couple tweaks:
Array.slice is not spec complient and browsers such as IE don't implement the method on the Array constructor.
We should use Array.prototype.slice.call
Also (index > this.length) ? index : this.length; could be Math.max(this.length, index)

  insert: function(index) {
    this.length = Math.max(this.length, index);
    index = index < 0 ? this.length : index;

    this.splice.apply(this, [index, 0]
      .concat(Array.prototype.slice.call(arguments, 1)));
    return this;
  }

Possible performance tweak (probably overkill here)

  insert: function(index) {
    var args = Array.prototype.slice.call(arguments, 1);
    this.length = Math.max(this.length, index);
    index = index < 0 ? this.length : index;

    if (args.length > 1)
      this.splice.apply(this, [index, 0].concat(args));
    else this.splice(index, 0, args[0]);
    return this;
  }