如何使用Javascript计算小数点后的数字？

Question

What do I have to change in the following code, so that the amount of digits after the decimal point is shown below the number?

 var operator = ['/']; function F1() { answer = document.getElementById("answer"); digits = document.getElementById("digits after decimal point"); rZ1 = Math.floor((Math.random() * 10)); rZ2 = Math.floor((Math.random() * 10) + 1); op = operator[Math.floor(Math.random() * 1)]; var a = parseFloat(eval(rZ1 + op + rZ2).toFixed(3)); var d = 3 if (a.toFixed(2) == a) { a = parseFloat(a.toFixed(2)); var d = 2; if (a.toFixed(1) == a) { a = parseFloat(a.toFixed(1)); var d = 1; } } answer.innerHTML = a; digits.innerHTML = d; }

 <button onclick="F1()"> New </button> <p> <label id="answer"> </label> </p> <label id="digits after decimal point"> </label>

Answer 1

You can just locate where the decimal point is with indexOf

 var operator = ['/']; function F1() { answer = document.getElementById("answer"); digits = document.getElementById("digits after decimal point"); rZ1 = Math.floor((Math.random() * 10)); rZ2 = Math.floor((Math.random() * 10) + 1); op = operator[Math.floor(Math.random() * 1)]; var a = parseFloat(eval(rZ1 + op + rZ2).toFixed(3)); var d = Math.max(0, (a+"").length - (a+".").indexOf(".") - 1); answer.textContent = a; digits.textContent = d; }

 <button onclick="F1()"> New </button> <p> <label id="answer"> </label> </p> <label id="digits after decimal point"> </label>