JavaScript replace() method dollar signs

It’s because $$ inserts a literal "$".

So, you need to use:

a = "aman/gupta";
a = a.replace("/", "$$$$"); // "aman$$gupta"

See the following special patterns:

Pattern	Inserts
`$$`	Inserts a "`$`".
`$&`	Inserts the matched substring.
$`	Inserts the portion of the string that precedes the matched substring.
`$'`	Inserts the portion of the string that follows the matched substring.
`$`n	Where n is a non-negative integer less than 100, inserts the _n_th parenthesized submatch string, provided the first argument was a RegExp object.
`$<`Name`>`	Where Name is a capturing group name. If the group is not in the match, or not in the regular expression, or if a string was passed as the first argument to `replace` instead of a regular expression, this resolves to a literal (e.g., "`$<Name>`").

Also you can use split and join for better performance and $ isn't special for those functions.

var a = "aman/gupta"
a = a.split('/').join('$$')
alert(a); // "aman$$gupta"

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