35 lines
1.2 KiB
JavaScript
35 lines
1.2 KiB
JavaScript
var root = require('./_root'),
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toInteger = require('./toInteger'),
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toNumber = require('./toNumber'),
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toString = require('./toString');
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/* Built-in method references for those with the same name as other `lodash` methods. */
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var nativeIsFinite = root.isFinite,
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nativeMin = Math.min;
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/**
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* Creates a function like `_.round`.
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*
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* @private
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* @param {string} methodName The name of the `Math` method to use when rounding.
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* @returns {Function} Returns the new round function.
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*/
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function createRound(methodName) {
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var func = Math[methodName];
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return function(number, precision) {
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number = toNumber(number);
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precision = precision == null ? 0 : nativeMin(toInteger(precision), 292);
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if (precision && nativeIsFinite(number)) {
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// Shift with exponential notation to avoid floating-point issues.
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// See [MDN](https://mdn.io/round#Examples) for more details.
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var pair = (toString(number) + 'e').split('e'),
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value = func(pair[0] + 'e' + (+pair[1] + precision));
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pair = (toString(value) + 'e').split('e');
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return +(pair[0] + 'e' + (+pair[1] - precision));
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}
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return func(number);
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};
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}
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module.exports = createRound;
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