Variables naming convention in Javascript & jQuery [duplicate]

Question

From what i understand, JavaScript requires variable to be defined using var keyword, and jQuery allows to define variables using $ symbol, I am wondering what added benefits does it bring when i define variable using jQuery, or is it purely preference? why will i use one convention over the other?

Also, what is the difference between the following variable declarations?

var foo
var $oo
$foo

“JavaScript requires variable to be defined using var keyword” – no, not necessarily. But without the var keyword they will always be global, not matter where that initialization occurs. And the $ part does not “define” a variable in itself, it is just part of the variable name. — C3roe
– C3roe, Commented Mar 19, 2015 at 4:57
See stackoverflow.com/questions/1916584/jquery-variable-syntax — jkd
– jkd, Commented Mar 19, 2015 at 4:57
Don't use $ in variable names. It's hideous. I know it's somewhat of a convention for jQuery users but it's a terrible one. There's just no need. You should have sensible enough names that you don't need a $ to know it's a jQuery object. — user1106925
– user1106925, Commented Mar 19, 2015 at 5:02
> JavaScript requires variable to be defined using var keyword, and jQuery allows to define variables using $ symbol this is wrong. JQuery is a (big) JavaScript framework, not a JavaScript "addon", you can't define a variable in JQuery, you just access to JQuery using $() - not $name w3schools.com/jquery/jquery_syntax.asp — Simone Sanfratello
– Simone Sanfratello, Commented Mar 19, 2015 at 5:12

Ryan · Accepted Answer · 2015-03-19 05:00:28Z

6

It is common to use a $ in front of the variable name when the variable is a jQuery object. Say for instance var $body = jQuery('body'); is a way to let other developers reading the code(and your future self) know they are dealing with a jQuery object instead of the body element directly. Definitely a preference thing, I would say decide what works best for your team and stick with it!

answered Mar 19, 2015 at 5:00

Ryan

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zozo · Accepted Answer · 2015-03-19 04:56:48Z

1

The dollar sign is not a variable definition. It is short for jQuery. More exactly $ === jQuery. Edit: This is in general, not in variable definition (as CBroe specified in comment).

So the fact that some use it for variable declaration is purely preference, and in my opinion a misguiding one. Or maybe they have php background and are used to the $varName definition from there.

About the differences, you have difference between:

var foo

and

foo

The first one is a local definition, while the second is global.

Example:

  function test() {
      var a = 2;
      b = 5;
  }

  test();
  console.log(a); // undefined
  console.log(b); // 5

answered Mar 19, 2015 at 4:56

zozo

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3 Comments

C3roe Over a year ago

“It is short for jQuery” – no, in $foo it is simply part of the variable name. (In $(…) it references the jQuery object, yes.)

zozo Over a year ago

That's what I meant, read the following line. "So the fact that some use it for variable declaration is purely preference, and in my opinion a misguiding one". Maybe I should rephrase that?

C3roe Over a year ago

Since OP used $foo as example, it might be misunderstood … but lets not nitpick, I just wanted to be clear about it. As for using it in variable names, which you consider “misguiding”, I think it makes sense when it is used to signify that a variable actually holds a jQuery object. var $elements = $('.selector')

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