修正javascript浮点数四舍五入时，0.085->0.08的问题

floatToFixed.js

/**
 * 浮点数四舍五入
 * 修正0.085->0.08的问题
 */
 Number.prototype.FloatToFixed = function(precision) {
    "use strict";
    var number = this;
    var str = Math.abs(number).toString(),
        negative = number < 0,
        lastNumber, mult;
    var dot_pos = str.indexOf('.');
    if (dot_pos == -1) {
        dot_pos = str.length;
    }
    str = str.substr(0, dot_pos + precision + 2);

    var str_decimals = str.substr((str.indexOf('.') == -1 ? str.length : str.indexOf('.')) + 1);
    if (str_decimals.length <= precision) {
        return (str * (negative ? -1 : 1)).toFixed(precision);
    }

    lastNumber = str.charAt(str.length - 1);
    str = str.substr(0, str.length - 1);
    if (lastNumber >= 5) {
        mult = Math.pow(10, str.length - str.indexOf('.') - 1);
        str = (+str + 1 / mult).toFixed(precision);
    }
    return str * (negative ? -1 : 1);
};