invalid escape in pattern HTML/Javascript

I am trying to make an <input> field that uses a pattern to check if the input is a valid windows file path.

The pattern I have is

/^(?:[\w]\:|\\)(\\[a-zA-Z_\-\s0-9\.()~!@#$%^&=+';,{}\[\]]+)+\.(exe)$/g

However, when putting this into the pattern attribute of an <input> field:

<input id="path" type="text" pattern="^(?:[\w]\:|\)(\[a-zA-Z_\-\s0-9\.()~!@#$%^&=+';,{}[]]+)+\.(exe)$">

An error is displayed in the console saying:

Pattern attribute value
^(?:[\w]\:|\\)(\\[a-zA-Z_\-\s0-9\.()~!@#$%^&=+';,{}\[\]]+)+\.(exe)$ is
not a valid regular expression:  Uncaught SyntaxError: Invalid regular
expression: /^(?:[\w]\:|\\)(\\[a-zA-Z_\-\s0-9\.()~!@#$%^&=+';,{}\[\]]+)+\.(exe)$/:
Invalid escape

I have tried several ways of writing this pattern, but none seem to work.

Solution

You only need to escape the characters in the character class that must be escaped otherwise, you will always get this error.

2023 Update:

Now, that pattern attribute is compiled with the v flag, escaping rules have become way stricter. See Valid with the RegExp u flag, but not with the v flag for more details.

The current solution will look like

pattern="(?:\w:|\\)(\\[\w\s.\(\)~!@#$%^&=+';,\{\}\[\]\-]+)+\.exe"

Note the [, {, }, ( and ) that are escaped now.

Original answer

Use

pattern="(?:\w:|\\)(\\[\w\s.()~!@#$%^&=+';,{}[\]-]+)+\.exe"

See the JSFiddle

Details:

The hyphen must be at the end of the character class
The ] inside the character class must be escaped
The [ and . must not be escaped
The : must never be esacaped, it is never a special character
[a-zA-Z0-9_] = \w
The pattern is always anchored by default, you need no ^ and $ anchors.