no-useless-escape

Disallow unnecessary escape characters

Escaping non-special characters in strings, template literals, and regular expressions doesn’t have any effect, as demonstrated in the following example:

let foo = "hol\a"; // > foo = "hola"
let bar = `${foo}\!`; // > bar = "hola!"
let baz = /\:/ // same functionality with /:/

Rule Details

This rule flags escapes that can be safely removed without changing behavior.

Examples of incorrect code for this rule:

/*eslint no-useless-escape: "error"*/

"\'";
'\"';
"\#";
"\e";
`\"`;
`\"${foo}\"`;
`\#{foo}`;
/\!/;
/\@/;
/[\[]/;
/[a-z\-]/;

Examples of correct code for this rule:

/*eslint no-useless-escape: "error"*/

"\"";
'\'';
"\x12";
"\u00a9";
"\371";
"xs\u2111";
`\``;
`\${${foo}}`;
`$\{${foo}}`;
/\\/g;
/\t/g;
/\w\$\*\^\./;
/[[]/;
/[\]]/;
/[a-z-]/;

Options

This rule has an object option:

• allowRegexCharacters - An array of characters that should be allowed to have unnecessary escapes in regular expressions. This is useful for characters like - where escaping can prevent accidental character ranges. For example, in /[0\-]/, the escape is technically unnecessary but helps prevent the pattern from becoming a range if another character is added later (e.g., /[0\-9]/ vs /[0-9]/).

allowRegexCharacters

Examples of incorrect code for the { "allowRegexCharacters": ["-"] } option:

/*eslint no-useless-escape: ["error", { "allowRegexCharacters": ["-"] }]*/

/\!/;
/\@/;
/[a-z\^]/;

Examples of correct code for the { "allowRegexCharacters": ["-"] } option:

/*eslint no-useless-escape: ["error", { "allowRegexCharacters": ["-"] }]*/

/[0\-]/;
/[\-9]/;
/a\-b/;

When Not To Use It

If you don’t want to be notified about unnecessary escapes, you can safely disable this rule.

Version

This rule was introduced in ESLint v2.5.0.

Resources

• Rule source
• Tests source