使用不同进制把数字格式化为指定的长度

<p id="demo">单击按钮来显示格式化的数字</p>

<button onclick="myFunction()">点我</button>

<script>

  function myFunction() {

    var num = new Number(13.3714);

    var a = num.toPrecision();

    var b = num.toPrecision(2);

    var c = num.toPrecision(3);

    var d = num.toPrecision(10);

    var n = a + "<br>" + b + "<br>" + c + "<br>" + d;

    var x = document.getElementById("demo");

    x.innerHTML = n

  }

</script>