Detect which word has been clicked on within a text

As far as I know, adding a span for each word is the only way to do this.

You might consider using Lettering.js, which handles the splitting for you. Though this won't really impact performance, unless your "splitting code" is inefficient.

Then, instead of binding .click() to every span, it would be more efficient to bind a single .click() to the container of the spans, and check event.target to see which span has been clicked.

Here are improvements for the accepted answer:

$(".clickable").click(function (e) {
    var selection = window.getSelection();
    if (!selection || selection.rangeCount < 1) return true;
    var range = selection.getRangeAt(0);
    var node = selection.anchorNode;
    var word_regexp = /^\w*$/;

    // Extend the range backward until it matches word beginning
    while ((range.startOffset > 0) && range.toString().match(word_regexp)) {
      range.setStart(node, (range.startOffset - 1));
    }
    // Restore the valid word match after overshooting
    if (!range.toString().match(word_regexp)) {
      range.setStart(node, range.startOffset + 1);
    }

    // Extend the range forward until it matches word ending
    while ((range.endOffset < node.length) && range.toString().match(word_regexp)) {
      range.setEnd(node, range.endOffset + 1);
    }
    // Restore the valid word match after overshooting
    if (!range.toString().match(word_regexp)) {
      range.setEnd(node, range.endOffset - 1);
    }

    var word = range.toString();
});​

And another take on @stevendaniel's answer:

$('.clickable').click(function(){
   var sel=window.getSelection();
   var str=sel.anchorNode.nodeValue,len=str.length, a=b=sel.anchorOffset;
   while(str[a]!=' '&&a--){}; if (str[a]==' ') a++; // start of word
   while(str[b]!=' '&&b++<len){};                   // end of word+1
   console.log(str.substring(a,b));
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<p class="clickable">The objective can also be achieved by simply analysing the
string you get from <code>sel=window.getSelection()</code>. Two simple searches for
the next blank before and after the word, pointed to by the current position
(<code>sel.anchorOffset</code>) and the work is done:</p>

<p>This second paragraph is <em>not</em> clickable. I tested this on Chrome and Internet explorer (IE11)</p>

Here's a solution that will work without adding tons of spans to the document (works on Webkit and Mozilla and IE9+):

https://jsfiddle.net/Vap7C/15/

    $(".clickable").click(function(e){
         s = window.getSelection();
         var range = s.getRangeAt(0);
         var node = s.anchorNode;
         
         // Find starting point
         while(range.toString().indexOf(' ') != 0) {                 
            range.setStart(node,(range.startOffset -1));
         }
         range.setStart(node, range.startOffset +1);
         
         // Find ending point
         do{
           range.setEnd(node,range.endOffset + 1);

        }while(range.toString().indexOf(' ') == -1 && range.toString().trim() != '');
        
        // Alert result
        var str = range.toString().trim();
        alert(str);
       });

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<p class="clickable">
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris rutrum ante nunc. Proin sit amet sem purus. Aliquam malesuada egestas metus, vel ornare purus sollicitudin at. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer porta turpis ut mi pharetra rhoncus. Ut accumsan, leo quis hendrerit luctus, purus nunc suscipit libero, sit amet lacinia turpis neque gravida sapien. Nulla facilisis neque sit amet lacus ornare consectetur non ac massa. In purus quam, imperdiet eget tempor eu, consectetur eget turpis. Curabitur mauris neque, venenatis a sollicitudin consectetur, hendrerit in arcu.
</p>

in IE8, it has problems because of getSelection. This link ( Is there a cross-browser solution for getSelection()? ) may help with those issues. I haven't tested on Opera.

I used https://jsfiddle.net/Vap7C/1/ from a similar question as a starting point. It used the Selection.modify function:

s.modify('extend','forward','word');
s.modify('extend','backward','word');

Unfortunately they don't always get the whole word. As a workaround, I got the Range for the selection and added two loops to find the word boundaries. The first one keeps adding characters to the word until it reaches a space. the second loop goes to the end of the word until it reaches a space.

This will also grab any punctuation at the end of the word, so make sure you trim that out if you need to.