Yang Guo | 4fd355c | 2019-09-19 08:59:03 | [diff] [blame] | 1 | var root = require('./_root'), |
| 2 | toInteger = require('./toInteger'), |
| 3 | toNumber = require('./toNumber'), |
| 4 | toString = require('./toString'); |
| 5 | |
| 6 | /* Built-in method references for those with the same name as other `lodash` methods. */ |
| 7 | var nativeIsFinite = root.isFinite, |
| 8 | nativeMin = Math.min; |
| 9 | |
| 10 | /** |
| 11 | * Creates a function like `_.round`. |
| 12 | * |
| 13 | * @private |
| 14 | * @param {string} methodName The name of the `Math` method to use when rounding. |
| 15 | * @returns {Function} Returns the new round function. |
| 16 | */ |
| 17 | function createRound(methodName) { |
| 18 | var func = Math[methodName]; |
| 19 | return function(number, precision) { |
| 20 | number = toNumber(number); |
| 21 | precision = precision == null ? 0 : nativeMin(toInteger(precision), 292); |
| 22 | if (precision && nativeIsFinite(number)) { |
| 23 | // Shift with exponential notation to avoid floating-point issues. |
| 24 | // See [MDN](https://mdn.io/round#Examples) for more details. |
| 25 | var pair = (toString(number) + 'e').split('e'), |
| 26 | value = func(pair[0] + 'e' + (+pair[1] + precision)); |
| 27 | |
| 28 | pair = (toString(value) + 'e').split('e'); |
| 29 | return +(pair[0] + 'e' + (+pair[1] - precision)); |
| 30 | } |
| 31 | return func(number); |
| 32 | }; |
| 33 | } |
| 34 | |
| 35 | module.exports = createRound; |