JavaScript實現數字前補“0”的五種方法示例

2024-05-06 16:47:30

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本文實例講述了JavaScript實現數字前補“0”的五種方法。分享給大家供大家參考，具體如下：

眾所周知JavaScript中的數字是沒有前置0的，因此需要我們自己進行操作來添加前置0，而且還得轉換成字符串。

<!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 數字前補“0”</title><body><script> //迭代方式實現 function padding1(num, length) {  for(var len = (num + "").length; len < length; len = num.length) {   num = "0" + num;  }  return num; } //遞歸方式實現 function padding2(num, length) {  if((num + "").length >= length) {   return num;  }  return padding2("0" + num, length) } //轉為小數 function padding3(num, length) {  var decimal = num / Math.pow(10, length);  //toFixed指定保留幾位小數  decimal = decimal.toFixed(length) + "";  return decimal.substr(decimal.indexOf(".")+1); } //填充截取法 function padding4(num, length) {  //這里用slice和substr均可  return (Array(length).join("0") + num).slice(-length); } //填充截取法 function padding5(num, length) {  var len = (num + "").length;  var diff = length - len;  if(diff > 0) {   return Array(diff).join("0") + num;  }  return num; } 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));  document.write("<br>");  document.write(padding4(num, length));  document.write("<br>");  document.write(padding5(num, length));  document.write("<br>"); } test(123, 10); test(1234567890123, 10);</script></body></html>

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