HTML - How do I insert a tag into each line of a
 block without hard coding?

Tags: javascript,jquery,html,css

Problem :

I was just trying to add line numbers at the beginning of source code using CSS. I realized the effect I wanted, as follows:

Effect implemented

However, the HTML code required continual use of <span>...</span> tags:

<pre class="code">
  <span>var links = document.getElementsByClassName("link");</span>
  <span>for(var i = 0; i &lt; links.length; i++){</span>
  <span>  links[i].onclick=function(){</span>
  <span>   alert(i+1);</span>
  <span>  };</span>

With the span tags positioned at home/end of lines I can let the line numbers show as expected. But I think there must be another better solution to prevent me adding all these span tags hard-coded, maybe using Javascript, or jQuery I don't mind but don't know how. Please help.

My problem is not how to display line numbers when the <span> tags are already there. Instead, I wanted to know if the origin HTML code contains NO <span> tags, how can I automatically add them into the suitable places and so I can apply the CSS styles.

Solution :

I have combined @Stewartside answer with what you have actually asked for.

Below you can see a simple plain JavaScript to replace any line in element with code class to be wrapped in span which applies @Stewartside css.

var codeElement = document.getElementsByClassName("code"); //array of code blocks
var formattedCode = codeElement[0].textContent.replace("\r\n", "\n").split("\n");
var codeLength = formattedCode.length;
formattedCode.forEach(function(line, index, array) {
  if (codeLength - 1 == index) return; 
  array[index] = "<span>" + line + "</span>";

codeElement[0].innerHTML = formattedCode.join("\n");

$(".code-jquery").each(function(index, codeElement) {
  var formattedCode = $(codeElement).html().replace("\r\n", "\n").split("\n");
  var codeLength = formattedCode.length;
  $.each(formattedCode, function(index, line) {
    if (codeLength - 1 == index) return;
    $(codeElement).append("<span>" + line + "</span>\n")
pre {
  background: #eee;
  counter-reset: section; /* Reset the counter to 0 for each new pre */
pre span:before {
  counter-increment: section; /* Increment the section counter*/
  content: counter(section); /* Display the counter */
  padding: 0 5px;
  border-right: 1px solid #777;
  margin-right: 5px;
  color: #777

pre.code-jquery span {
  color: green;
<pre class="code">
  var links = document.getElementsByClassName("link");
  for(var i = 0; i &lt; links.length; i++) {
    links[i].onclick = function() {

//jQuery version
<script src=""></script>
<pre class="code-jquery">
  var links = document.getElementsByClassName("link");
  for(var i = 0; i &lt; links.length; i++) {
    links[i].onclick = function() {

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