mirror of https://github.com/jkjoy/sunpeiwen.git
64 lines
1.7 KiB
JavaScript
64 lines
1.7 KiB
JavaScript
'use strict';
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// http://www.2ality.com/2013/10/safe-integers.html
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// http://es6.ruanyifeng.com/#docs/number
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exports.MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER || Math.pow(2, 53) - 1;
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exports.MIN_SAFE_INTEGER = -exports.MAX_SAFE_INTEGER;
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var MAX_SAFE_INTEGER_STR = exports.MAX_SAFE_INTEGER_STR = String(exports.MAX_SAFE_INTEGER);
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var MAX_SAFE_INTEGER_STR_LENGTH = MAX_SAFE_INTEGER_STR.length;
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/**
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* Detect a number string can safe convert to Javascript Number.
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*
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* @param {String} s number format string, like `"123"`, `"-1000123123123123123123"`
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* @return {Boolean}
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*/
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exports.isSafeNumberString = function isSafeNumberString(s) {
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if (s[0] === '-') {
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s = s.substring(1);
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}
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if (s.length < MAX_SAFE_INTEGER_STR_LENGTH ||
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(s.length === MAX_SAFE_INTEGER_STR_LENGTH && s <= MAX_SAFE_INTEGER_STR)) {
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return true;
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}
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return false;
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};
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/**
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* Convert string to Number if string in safe Number scope.
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*
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* @param {String} s number format string.
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* @return {Number|String} success will return Number, otherise return the original string.
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*/
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exports.toSafeNumber = function toSafeNumber(s) {
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if (typeof s === 'number') {
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return s;
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}
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return exports.isSafeNumberString(s) ? Number(s) : s;
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};
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/**
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* Produces a random integer between the inclusive `lower` and `upper` bounds.
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*
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* @param {Number} lower The lower bound.
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* @param {Number} upper The upper bound.
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* @return {Number} Returns the random number.
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*/
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exports.random = function random(lower, upper) {
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if (lower === undefined && upper === undefined) {
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return 0;
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}
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if (upper === undefined) {
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upper = lower;
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lower = 0;
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}
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var temp;
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if (lower > upper) {
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temp = lower;
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lower = upper;
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upper = temp;
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}
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return Math.floor(lower + Math.random() * (upper - lower));
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};
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