jQuery: Why prepend a $ to variable name?

Question

I am trying to learn jQuery and I came across this line in an example.

var $title = $(tag).attr('title');

Can someone please tell me what the prepended $ is for in $title.

The example seems to work fine if I replace $title with just title.

I understand this is probably a stupid question but it is a waste of time googling for "purpose of $"

Many thanks.

Answer 1

It doesn't "mean" anything. The $ character is a legal character in Javascript variable names.

However, there is a convention (which isn't universal) of using $ as a prefix to any variable that points to a jQuery selection.

You give the example:

var $title = $(tag).attr('title');

This is a bad use of the $ character, according to this convention. $title is a string, not a jQuery selection.

This would be a correct use of the character:

var $el = $(tag);
var title = $el.attr('title');

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Otherwise, a big reason for the prevalence of the $ character is that it is mandatory in PHP, and there is a big overlap between jQuery and PHP programmers.

Answer 2

I think people use it as a convention for 'things I looked up with jQuery that I want to hold onto without needing to look up again'.

The one you see most often is var $this = $(this)