A brief analysis of floating point arithmetic problems in js_javascript skills

How are floating point operations performed in js?

For example: var a=0.69;

I want to get 6.9 by writing var c=a*10;

alert(c); The result is: 6.8999999999999995

After searching online, some netizens said that this is a JS floating point calculation bug and found a solution:

Method 1: Have js custom function

Copy code Code As follows: //Addition function, used to obtain accurate addition results //Explanation: The addition result of JavaScript will have errors, which will be more obvious when adding two floating point numbers. This function returns a more accurate addition result. //Call: accAdd(arg1,arg2) //Return value: the exact result of arg1 plus arg2 function accAdd(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 (arg1*m arg2*m)/ m } //Add an add method to the Number type to make it more convenient to call. Number.prototype.add = function (arg){ return accAdd(arg,this); }

//Addition function, used to obtain accurate addition results //Explanation: The addition result of JavaScript will have errors, which will be more obvious when adding two floating point numbers. This function returns a more accurate addition result. //Call: accAdd(arg1,arg2) //Return value: the exact result of arg1 plus arg2 function accSub(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)); //last modify by deeka //Dynamic control precision length n=(r1>=r2)?r1:r2; return ((arg1*m-arg2*m)/m).toFixed(n); }

//Division function, used to obtain accurate division results //Explanation: The division result of JavaScript will have errors, which will be more obvious when dividing two floating point numbers. This function returns a more accurate division result. //Call: accDiv(arg1,arg2) //Return value: the exact result of dividing arg1 by arg2 function accDiv(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 (r1/r2)*pow(10,t2-t1); } } //Add a div method to the Number type to make it more convenient to call. Number.prototype.div = function (arg){ return accDiv(this, arg); }

//Multiplication function, used to obtain accurate multiplication results //Explanation: The multiplication result of JavaScript will have errors, which will be more obvious when two floating point numbers are multiplied. This function returns a more accurate multiplication result. //Call: accMul(arg1,arg2) //Return value: the exact result of arg1 multiplied by arg2 function accMul(arg1,arg2) { var m=0, s1=arg1.toString(),s2=arg2.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) } //Add a mul method to the Number type to make it more convenient to call. Number.prototype.mul = function (arg){ return accMul(arg, this); }

var a=0.69; var b=10; alert(a*b);//6.8999999999999995 alert((a*100)/10);

Just call the function directly. Method 2: If you know the number of decimal places, you can consider amplifying the floating point number to an integer (and finally dividing it by the corresponding multiple), and then Perform calculation operations so that you can get the correct result

alert(11*22.9);//Get 251.89999999999998 alert(11*(22.9*10)/10);//Get 251.9