Javascript Unexpected control character(s) in regular expression

Question

My ESlint throws the error Unexpected control character(s) in regular expression: \x08 no-control-regex for my regular expression let regex = new RegExp("^[0-9a-zA-Z \b]+$");

If i remove \b from my regEx the error is not thrown. Why is this happening? How can i remove the error?

Answer 1

The rule no-control-regex is on.

This rule is enabled by default when you inherit rules from eslint:recommended

"extends": "eslint:recommended"

Reason why it's enabled by default:

Control characters are special, invisible characters in the ASCII range 0-31. These characters are rarely used in JavaScript strings so a regular expression containing these characters is most likely a mistake.

To disable this rule, add on your eslint config

"rules": {
  "no-control-regex": 0
}

Answer 2

The reasons why ESLint throwing error:

1. Lint rule no-control-regex is on.
2. The expression in string is not properly escaped and therefore contains control characters. See the following code:

// This prints: ^[0-9a-zA-Z]+$
// Notice that the space character and \b is missing
console.log("^[0-9a-zA-Z \b]+$")

The right way to fix the error is to escape the string properly.

let regex = new RegExp("^[0-9a-zA-Z \\b]+$");