Simple function to dynamically create an array of a given length where the values are equal to the indices. (407 bytes; 87 bytes minified)

gistfile1.js

/**
 * Creates an array in which each value stored in the array represets the value's index (zero-based).
 * @param {number} len - Length of array to produce.
 * @returns {array} The resulting array.
 */
function arrayOfNumbers(len) {
	/*
	 * You could replace Number with eval and save 2 additional bytes,
	 * however that is less secure and probalby not worth the 2 bytes.
	 *
	 * Date is used below to save 2 bytes. This works since Date.call.bind
	 * and Number.call.bind both bind Function.call, so it doesn't matter
	 * which is used.
	 */
	return Array.apply(0, Array(len)).map(Date.call.bind(Number));
}