Just wondering if it is valid to use $ in front of variable name in JavaScript (like PHP).
So can I do something like this:
var $x = 1; // Is this valid with the $ in front?
var y = 2; // This is valid JavaScript
I have tested a little and it seems to work, but want to make sure it is valid and will work across all browsers before I do it.
Yes, it has always been valid since the first edition of the ECMAScript language specification.
According to the 10th edition of the ECMAScript language specification published in 2019 (see: ECMAScript Language: Lexical Grammar - Names and Keywords), the grammar for variable names is:
IdentifierName::
IdentifierStart
IdentifierName IdentifierPart
IdentifierStart::
UnicodeIDStart
$
_
\ UnicodeEscapeSequence
IdentifierPart::
UnicodeIDContinue
$
\ UnicodeEscapeSequence
<ZWNJ>
<ZWJ>
...
As you can see, it is valid to have $ anywhere in the variable name.
This has always been the case since the first edition of ECMAScript standard published in 1997. Section 4.5 Identifiers from the first edition says:
An identifier is a character sequence of unlimited length, where each character in the sequence must be a letter, a decimal digit, an underscore (_) character, or a dollar sign ($) character, and the first character may not be a decimal digit.
Javascript variable names can begin with a letter, $ or _ . As long as you dont start your variable name with a number, your good to go.
Valid, yes, but a code style not usually used unless it has meaning.
I've seen some folks use $someVar to indicate a jQuery-decorated element, for example. (Because, jQuery by default uses $ for its name.)
I would not recommend using it unless you have a specific reason, and are consistent in your codebase.
Yes, Javascript accepts $ and _ as variable names. It works and it is valid in any browser.Check it here
const/letrather thanvar. Their scope is much more clear/less quirky.