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