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作者：vkvi 来源：ITPOW（原创） 日期：2014-12-12

代码最初源自网上，但网上的代码格式之乱，不堪入目，作了调整和优化，现公布出来，希望对大家有用。

Math.add = function(v1, v2) { ///<summary>精确计算加法。语法：Math.add(v1, v2)</summary> ///<param name="v1" type="number">操作数。</param> ///<param name="v2" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> var r1, r2, m; try { r1 = v1.toString().split(".")[1].length; } catch (e) { r1 = 0; } try { r2 = v2.toString().split(".")[1].length; } catch (e) { r2 = 0; } m = Math.pow(10, Math.max(r1, r2)); return (v1 * m + v2 * m) / m; } Number.prototype.add = function(v) { ///<summary>精确计算加法。语法：number1.add(v)</summary> ///<param name="v" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> return Math.add(v, this); } Math.sub = function(v1, v2) { ///<summary>精确计算减法。语法：Math.sub(v1, v2)</summary> ///<param name="v1" type="number">操作数。</param> ///<param name="v2" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> return Math.add(v1, -v2); } Number.prototype.sub = function(v) { ///<summary>精确计算减法。语法：number1.sub(v)</summary> ///<param name="v" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> return Math.sub(this, v); } Math.mul = function(v1, v2) { ///<summary>精确计算乘法。语法：Math.mul(v1, v2)</summary> ///<param name="v1" type="number">操作数。</param> ///<param name="v2" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> var m = 0; var s1 = v1.toString(); var s2 = v2.toString(); try { m += s1.split(".")[1].length; } catch (e) { } try { m += s2.split(".")[1].length; } catch (e) { } return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m); } Number.prototype.mul = function(v) { ///<summary>精确计算乘法。语法：number1.mul(v)</summary> ///<param name="v" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> return Math.mul(v, this); } Math.div = function(v1, v2) { ///<summary>精确计算除法。语法：Math.div(v1, v2)</summary> ///<param name="v1" type="number">操作数。</param> ///<param name="v2" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> var t1 = 0; var t2 = 0; var r1, r2; try { t1 = v1.toString().split(".")[1].length; } catch (e) { } try { t2 = v2.toString().split(".")[1].length; } catch (e) { } with (Math) { r1 = Number(v1.toString().replace(".", "")); r2 = Number(v2.toString().replace(".", "")); return (r1 / r2) * pow(10, t2 - t1); } } Number.prototype.div = function(v) { ///<summary>精确计算除法。语法：number1.div(v)</summary> ///<param name="v" type="number">操作数。</param> ///<returns type="number">计算结果。</returns> return Math.div(this, v); }

怎么测试呢？试试下面的结果：

alert(1 + 0.91); var m = 1; alert(m.add(0.91));