CodingForums.com - easy numbered array generation

i have been search forever for a way to make a numbered array using only native functions and without looping.

i had figured out a long, convoluted way of doing it with eval and bind(), but it was not pretty.

the one trick to this native functionality is that you have to specify a number one more than the ceiling you want, but that's not the end of the world...

the method is related to the popular String repeat trick:

Code:

Array(101).join(",").split(",").join("hello world \t")

you can even shorten the code below by removing ".map(Number)" if you don't need "real Number" numbers, but simply a list of digits.

here is the numbered array code:

Code:

Object.keys( new String( Array(101) ) ).map(Number)

result

Code:

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]

for you cut-and-paste pleasure, here are some working reusables:

as a function

Code:

function arr(n) {

        return Object.keys(new String(Array(n - -1))).map(Number);

}

usage

Code:

arr(10) // === [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]



arr(12).map(arr).join("\n") /* ==="



0

0,1

0,1,2

0,1,2,3

0,1,2,3,4

0,1,2,3,4,5

0,1,2,3,4,5,6

0,1,2,3,4,5,6,7

0,1,2,3,4,5,6,7,8

0,1,2,3,4,5,6,7,8,9

0,1,2,3,4,5,6,7,8,9,10 " 



*/

as a mutating array prototype

Code:

Array.prototype.numbered = function _numbered(n) {

        n = n || this.length;

        this.length = 0;

        this.push.apply(this, Object.keys(new String(Array(n - -1))).map(Number));

        return this;

};//end [].numbered()

and as a hidden mutating array prototype

Code:

Object.defineProperty(Array.prototype,"numbered", function _numbered(n) {

        n = n || this.length;

        this.length = 0;

        this.push.apply(this, Object.keys(new String(Array(n - -1))).map(Number));

        return this;

});//end [].numbered()

usage

Code:

["a","b","c"].numbered() // === [0, 1, 2]



["a","b","c"].numbered(10) // === [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]



Array().numbered(10) // === [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]