js怎么补齐数字(2)-木庄网络博客

方法一：迭代方式实现

function PrefixInteger(num, length) {
  for(var len = (num + "").length; len < length; len = num.length) {
   num = "0" + num;
   }
  return num;
}

方法二：转为小数

function PrefixInteger(num, length) {
 var decimal = num / Math.pow(10, length);
  //toFixed指定保留几位小数
  decimal = decimal.toFixed(length) + "";
  return decimal.substr(decimal.indexOf(".")+1);
}

方法三：更高效

function PrefixInteger(num, length) {
 return (Array(length).join('0') + num).slice(-length);  
}

测试：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>JavaScript 数字前补“0”</title>
<body>
<script>
 //迭代方式实现
 function padding1(num, length) {
  for(var len = (num + "").length; len < length; len = num.length) {
   num = "0" + num;
  }
  return num;
 }
//转为小数
 function padding2(num, length) {
  var decimal = num / Math.pow(10, length);
  //toFixed指定保留几位小数
  decimal = decimal.toFixed(length) + "";
  return decimal.substr(decimal.indexOf(".")+1);
 }
 //填充截取法
 function padding3(num, length) {
  //这里用slice和substr均可
  return (Array(length).join("0") + num).slice(-length);
 }
 
 function test(num, length) {
  document.write(padding1(num, length));
  document.write("<br>");
  document.write(padding2(num, length));
  document.write("<br>");
  document.write(padding3(num, length));
 }
 test(123, 10);
</script>
</body>
</html>