精确计算插件 · 前端

``` Number.prototype.toFixed = function(j) { var h = this + ""; if (!j) { j = 0 } if (h.indexOf(".") == -1) { h += "." } h += new Array(j + 1).join("0"); if (new RegExp("^(-|\\+)?(\\d+(\\.\\d{0," + (j + 1) + "})?)\\d*$").test(h)) { var h = "0" + RegExp.$2, g = RegExp.$1, e = RegExp.$3.length, c = true; if (e == j + 2) { e = h.match(/\d/g); if (parseInt(e[e.length - 1]) > 4) { for (var f = e.length - 2; f >= 0; f--) { e[f] = parseInt(e[f]) + 1; if (e[f] == 10) { e[f] = 0; c = f != 1 } else { break } } } h = e.join("").replace(new RegExp("(\\d+)(\\d{" + j + "})\\d$"), "$1.$2") } if (c) { h = h.substr(1) } return (g + h).replace(/\.$/, "") } return this + "" }; var CalcEval = function() {}; CalcEval.prototype.eval = function(str) { var isRetStr = str.match(new RegExp(/^".+"$/g)) != null; if (isRetStr == true) { str = str.replace(/^"|"$/g, "") } var bracketsList = this.matchOutBrackets(str); for (var i = 0; i < bracketsList.length; i++) { var newCalc = bracketsList[i]; var calcStr = this.eval(newCalc.str.replace(/^$|$$/g, "")); str = str.replace(newCalc.str, calcStr) } var errorObj = new Array(); while (1) { var multObj = this.matchExp(str, "/"); if (multObj == null) { break } var v = this.executeDivi(multObj.firstValue, multObj.secondValue); if (v == "NaN") { var t = "T" + new Date().getTime(); errorObj.push({ Name: t, Exp: multObj.str }); str = str.replace(multObj.str, t) } else { str = str.replace(multObj.str, v) } } while (1) { var multObj = this.matchExp(str, "*"); if (multObj == null) { break } var v = this.executeMult(multObj.firstValue, multObj.secondValue); if (v == "NaN") { var t = "T" + new Date().getTime(); errorObj.push({ Name: t, Exp: multObj.str }); str = str.replace(multObj.str, t) } else { str = str.replace(multObj.str, v) } } while (1) { var multObj = this.matchExp(str, "+"); if (multObj == null) { break } var v = this.executeAddi(multObj.firstValue, multObj.secondValue); if (v == "NaN" || isNaN(v)) { var t = "T" + new Date().getTime(); errorObj.push({ Name: t, Exp: multObj.str }); str = str.replace(multObj.str, t) } else { str = str.replace(multObj.str, v) } } while (1) { var multObj = this.matchExp(str, "-"); if (multObj == null) { break } var v = this.executeSubt(multObj.firstValue, multObj.secondValue); if (v == "NaN") { var t = "T" + new Date().getTime(); errorObj.push({ Name: t, Exp: multObj.str }); str = str.replace(multObj.str, t) } else { str = str.replace(multObj.str, v) } } for (var i = errorObj.length - 1; i >= 0; i--) { var ex = errorObj[i]; str = str.replace(ex.Name, ex.Exp) } while (1) { var multObj = str.match(/\d*={2,3}\d*/g); if (multObj == null) { break } var v = eval(multObj[0]); str = str.replace(multObj[0], v) } if (isRetStr == true) { try { return eval('"' + str + '"') } catch(e) {} try { return eval(str) } catch(e) {} return str } if (str.match(/(^true$)|(^false$)/g)) { return str === "true" } if (!isNaN(Number(str))) { return Number(str) } try { return eval(str) } catch(e) {} return str }; CalcEval.prototype.matchOutBrackets = function(f) { var h = new Array(); if (f == null) { return h } if (typeof f != "string") { f = f + "" } var d = f.split(""); var a = 0; var g = false; var b = -1; for (var c = 0; c < d.length; c++) { if (d[c] == "(") { a++; g = true; if (b == -1) { b = c } } if (d[c] == ")") { a-- } if (g == true && a == 0) { var e = new Object(); e.str = f.substring(b, c + 1); e.firstIndex = b; e.lastIndex = c + 1; h.push(e); b = -1; g = false; a = 0 } } return h }; CalcEval.prototype.matchExp = function(l, f) { var j = null; if (l == null) { return retList } if (typeof l != "string") { l = l + "" } var k = l.split(""); var c = 0; var b = 0; var g = ""; var e = ""; var a = ""; var d = false; for (var h = 0; h <= k.length; h++) { if (k[h] == "+" || k[h] == "-" || k[h] == "*" || k[h] == "/" || k[h] == "%" || h == k.length) { if (a == "" && k[h] == "-") { a += k[h]; continue } if (d == true) { e = a; b = h; j = new Object(); j.firstIndex = c; j.secondIndex = b; j.str = l.substring(c, b); j.firstValue = Number(g); j.secondValue = Number(e); break } if (k[h] == null) { break } if (k[h] == f) { d = true; g = a; a = "" } else { a = ""; c = -1 } } else { a += k[h]; if (c == -1) { c = h } } } return j }; CalcEval.prototype.executeMult = function(d, b) { var a = 0, f = d.toString(), c = b.toString(); try { a += f.split(".")[1].length } catch(g) {} try { a += c.split(".")[1].length } catch(g) {} return Number(f.replace(".", "")) * Number(c.replace(".", "")) / Math.pow(10, a) }; CalcEval.prototype.executeDivi = function(arg1, arg2) { var t1 = 0, t2 = 0, r1, r2; try { t1 = arg1.toString().split(".")[1].length } catch(e) {} try { t2 = arg2.toString().split(".")[1].length } catch(e) {} with(Math) { r1 = Number(arg1.toString().replace(".", "")); r2 = Number(arg2.toString().replace(".", "")); return this.executeMult(r1 / r2, pow(10, t2 - t1)) } }; CalcEval.prototype.executeAddi = function(arg1, arg2) { var r1, r2, m; try { r1 = arg1.toString().split(".")[1].length } catch(e) { r1 = 0 } try { r2 = arg2.toString().split(".")[1].length } catch(e) { r2 = 0 } m = Math.pow(10, Math.max(r1, r2)); return (this.eval(arg1 + "*" + m) + this.eval(arg2 + "*" + m)) / m }; CalcEval.prototype.executeSubt = function(arg1, arg2) { var r1, r2, m, n; try { r1 = arg1.toString().split(".")[1].length } catch(e) { r1 = 0 } try { r2 = arg2.toString().split(".")[1].length } catch(e) { r2 = 0 } m = Math.pow(10, Math.max(r1, r2)); n = (r1 >= r2) ? r1: r2; return ((this.eval(arg1 + "*" + m) - this.eval(arg2 + "*" + m)) / m).toFixed(n) }; ```