naming conventions - Why do I see JavaScript variables prefixed with $? - Stack Overflow

admin管理员组

文章数量:1201375

This is sort of a meta-question. Many snippets of JavaScript I've seen here on SO are named with a dollar sign prefix (for example, $id on the second line of the snippet shown in this question). I'm not referring to jQuery or other libraries. I am well aware that this is valid, but it seems awkward to do when not necessary. Why do people name their variables like this? Is it just familiarity with a server-side language like PHP carrying over into their JavaScript code?

I thought perhaps it was to identify a variable as being a jQuery object, for example when you save the result of a selection to a variable in order to eliminate duplicate selections later on, but I haven't seen any consistent convention.

This is sort of a meta-question. Many snippets of JavaScript I've seen here on SO are named with a dollar sign prefix (for example, $id on the second line of the snippet shown in this question). I'm not referring to jQuery or other libraries. I am well aware that this is valid, but it seems awkward to do when not necessary. Why do people name their variables like this? Is it just familiarity with a server-side language like PHP carrying over into their JavaScript code?

I thought perhaps it was to identify a variable as being a jQuery object, for example when you save the result of a selection to a variable in order to eliminate duplicate selections later on, but I haven't seen any consistent convention.

• javascript
• naming-conventions

Share Improve this question Follow edited May 23, 2017 at 10:27 CommunityBot 111 silver badge asked Feb 3, 2010 at 4:03 Jonathon FaustJonathon Faust 12.5k44 gold badges5252 silver badges6363 bronze badges

Add a comment  | 

3 Answers 3

Sorted by: Reset to default 19

Syntactically, the dollar sign itself means nothing -- to the interpreter, it's just another character, like _ or q. But a lot of people using jQuery and other similar frameworks will prefix variables that contain a jQuery object with a $ so that they are easily identified, and thus not mixed up with things like integers or strings. You could just as easily adopt the same convention by prefixing such variables with jq_ and it would have the same effect.

In effect, it is a crude sort of Hungarian notation.

I will sometimes prefix a variable name with $ to indicate that it is a jQuery-wrapped element (most often when I'm using $(this) in a function a lot, I will assign that to $this).

Part of where the lack of convention may come from is people copy-pasting code together that uses different conventions, thus producing inconsistent code.

Also, sometimes (rarely I hope) people who program in PHP a lot will put $'s at the beginning of their variable names out of habit.

I suspect the person in that example was just copying the jQuery pattern, or is used to PHP/Perl, without really understanding that it isn't necessary and has no special meaning.

However, I have seen [experienced] programmers use it for variable names that are reserved keywords, such as $class or $this. Or even for globals. It's really a personal preference more than anything, in that case.

本文标签： naming conventionsWhy do I see JavaScript variables prefixed with Stack Overflow