Pattern with regex not working as expected

I have really liked using knockout-validation. I think it works well. I've just come across one small thing (that has been verified by someone else). I have a knockout observable (string) with the following validation extend definition
```
pattern: {
message: this.gui.validationCannotInclude,
params: '^[^\/\\\^\$\.\|\?\*\+\(\)\"\']+$'
}
```
It works fine detecting all of the escaped characters, except \ - it even catches /. I've checked the regex in https://www.regextester.com/ and it seems correct. Attempted rewriting the regex to put the backslash elsewhere in the definition, but it doesn't help.

The complete definition on this observable is:
```
ko.observable(this.Name).extend({
required: {
message: this.gui.validationRequired
},
maxLength: {
params: 50,
message: this.gui.validationLongerThan50
},
pattern: {
message: this.gui.validationCannotInclude,
params: '^[^\/\\\^\$\.\|\?\*\+\(\)\"\']+$'
}
```
Thank you.

Start with the pattern validator used by the knockout observable's extend definition and reproduce the supplied regular expression, focusing on why it does not detect a backslash while detecting the other escaped characters. Confirm the expected behavior against the complete required, maxLength, and pattern definition; done means backslashes are detected without regressing the other listed characters.

Written by the indexing model from the issue text.