What is Join() in jQuery?

What is Join() in jquery? for example:

var newText = $("p").text().split(" ").join("</span> <span>"); 

That's not a jQuery function - it's the regular Array.join function.

It converts an array to a string, putting the argument between each element.

You would probably use your example like this

var newText = "<span>" + $("p").text().split(" ").join("</span> <span>") + "</span>";

This will put span tags around all the words in you paragraphs, turning

<p>Test is a demo.</p>

into

<p><span>Test</span> <span>is</span> <span>a</span> <span>demo.</span></p>

I do not know what the practical use of this could be.

The practical use of this construct? It is a javascript replaceAll() on strings.

var s = 'stackoverflow_is_cool';  
s = s.split('_').join(' ');  
console.log(s);

will output:

stackoverflow is cool

join is not a jQuery function .Its a javascript function.

The join() method joins the elements of an array into a string, and returns the string.The elements will be separated by a specified separator. The default separator is comma (,).

http://www.w3schools.com/jsref/jsref_join.asp

I use join to separate the word in array with "and, or , / , &"

EXAMPLE

HTML

<p>London Mexico Canada</p>
<div></div>

JS

 newText = $("p").text().split(" ").join(" or ");
 $('div').text(newText);

Results

London or Mexico or Canada

A practical example using a jQuery example might be

 var today = new Date();
 $('#'+[today.getMonth()+1, today.getDate(), today.getFullYear()].join("_")).whatever();

I do that in a calendar tool that I am using, this way on the page load, I can do certain things with today's date.