| var isIterateeCall = require('../internal/isIterateeCall'); |
| |
| /* Native method references for those with the same name as other `lodash` methods. */ |
| var nativeCeil = Math.ceil, |
| nativeMax = Math.max; |
| |
| /** |
| * Creates an array of numbers (positive and/or negative) progressing from |
| * `start` up to, but not including, `end`. If `end` is not specified it's |
| * set to `start` with `start` then set to `0`. If `end` is less than `start` |
| * a zero-length range is created unless a negative `step` is specified. |
| * |
| * @static |
| * @memberOf _ |
| * @category Utility |
| * @param {number} [start=0] The start of the range. |
| * @param {number} end The end of the range. |
| * @param {number} [step=1] The value to increment or decrement by. |
| * @returns {Array} Returns the new array of numbers. |
| * @example |
| * |
| * _.range(4); |
| * // => [0, 1, 2, 3] |
| * |
| * _.range(1, 5); |
| * // => [1, 2, 3, 4] |
| * |
| * _.range(0, 20, 5); |
| * // => [0, 5, 10, 15] |
| * |
| * _.range(0, -4, -1); |
| * // => [0, -1, -2, -3] |
| * |
| * _.range(1, 4, 0); |
| * // => [1, 1, 1] |
| * |
| * _.range(0); |
| * // => [] |
| */ |
| function range(start, end, step) { |
| if (step && isIterateeCall(start, end, step)) { |
| end = step = undefined; |
| } |
| start = +start || 0; |
| step = step == null ? 1 : (+step || 0); |
| |
| if (end == null) { |
| end = start; |
| start = 0; |
| } else { |
| end = +end || 0; |
| } |
| // Use `Array(length)` so engines like Chakra and V8 avoid slower modes. |
| // See https://youtu.be/XAqIpGU8ZZk#t=17m25s for more details. |
| var index = -1, |
| length = nativeMax(nativeCeil((end - start) / (step || 1)), 0), |
| result = Array(length); |
| |
| while (++index < length) { |
| result[index] = start; |
| start += step; |
| } |
| return result; |
| } |
| |
| module.exports = range; |