js小数精确计算实现

Number.prototype.add = function (arg) {
    var r1, r2, m,p1,p2,p3,p4;
    try {var s1=this.toString().split(".");r1 = s1[1].length;p1=s1[0];p2=s1[1]/Math.pow(10,r1) } catch (e) { r1 = 0 ;p1=this;p2=0}
    try {var s2=arg.toString().split(".");r2 = s2[1].length;p3=s2[0];p4=s2[1]/Math.pow(10,r2) } catch (e) { r2 = 0 ;p1=arg;p2=0}
    m = Math.pow(10, Math.max(r1, r2))
    return (p1*m+p2*m+p3*m+p4*m)/m;
}