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