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Detailed example of how to add line numbers to Textarea text boxes in JavaScript

巴扎黑Original: 2017-09-08 11:28:342645browse

本文实例讲述了JS给Textarea文本框添加行号的方法。分享给大家供大家参考。具体如下：

这里使用JS实现让Textarea文本框显示行号的功能，每一行的前面都会有下数字序号，如果用来显示代码的话，可以直接找到某一行，如果不显示行号，则还要自己手功去查，想要此功能，你只需设置好TextArea ID，并加入代码中的JavaScript代码部分即可，文本框的长宽则是由CSS来控制的，你可试着修改一下，长宽的显示要与JS相匹配。

运行效果截图如下：

在线演示地址如下：

http://demo.jb51.net/js/2015/js-textarea-show-row-num-codes/

具体代码如下：

&lt;html> 
&lt;head>
&lt;title>Js给文本框添加行号功能&lt;/title>
&lt;style type="text/css">
 #codeTextarea{width: 500px;height: 310px;}
.textAreaWithLines{font-family: courier;border: 1px solid #ddd;}
.textAreaWithLines textarea,.textAreaWithLines p{border: 0px;line-height: 120%;font-size: 12px;}
.lineObj{color: #666;}
&lt;/style>
&lt;script type="text/javascript">
var lineObjOffsetTop = 2;
function createTextAreaWithLines(id)
{
  var el = document.createElement("p");
  var ta = document.getElementById(id);
  ta.parentNode.insertBefore(el,ta);
  el.appendChild(ta);
  el.className="textAreaWithLines";
  el.style.width = (ta.offsetWidth + 30) + "px";
  ta.style.position = "absolute";
  ta.style.left = "30px";
  el.style.height = (ta.offsetHeight + 2) + "px";
  el.style.overflow="hidden";
  el.style.position = "relative";
  el.style.width = (ta.offsetWidth + 30) + "px";
  var lineObj = document.createElement("p");
  lineObj.style.position = "absolute";
  lineObj.style.top = lineObjOffsetTop + "px";
  lineObj.style.left = "0px";
  lineObj.style.width = "27px";
  el.insertBefore(lineObj,ta);
  lineObj.style.textAlign = "right";
  lineObj.className="lineObj";
  var string = "";
  for(var no=1;no&lt;20;no++){
   if(string.length>0)string = string + "&lt;br>";
   string = string + no;
  }
   ta.onkeydown = function() { positionLineObj(lineObj,ta); };
   ta.onmousedown = function() { positionLineObj(lineObj,ta); };
   ta.onscroll = function() { positionLineObj(lineObj,ta); };
   ta.onblur = function() { positionLineObj(lineObj,ta); };
   ta.onfocus = function() { positionLineObj(lineObj,ta); };
   ta.onmouseover = function() { positionLineObj(lineObj,ta); };
   lineObj.innerHTML = string;
  }
function positionLineObj(obj,ta)
{
   obj.style.top = (ta.scrollTop * -1 + lineObjOffsetTop) + "px";  
}
&lt;/script>
&lt;/head>  
&lt;body>
&lt;form>
&lt;textarea id="codeTextarea">&lt;/textarea>
&lt;/form>
&lt;script type="text/javascript">
createTextAreaWithLines("codeTextarea");
&lt;/script>
&lt;/body>
&lt;/html>

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