require-unicode-regexp
Enforce the use of u
flag on RegExp
Some problems reported by this rule are manually fixable by editor suggestions
RegExp u
flag has two effects:
-
Make the regular expression handling UTF-16 surrogate pairs correctly.
Especially, character range syntax gets the correct behavior.
/^[๐]$/.test("๐") //โ false /^[๐]$/u.test("๐") //โ true
-
Make the regular expression throwing syntax errors early as disabling Annex B extensions.
Because of historical reason, JavaScript regular expressions are tolerant of syntax errors. For example,
/\w{1, 2/
is a syntax error, but JavaScript doesnโt throw the error. It matches strings such as"a{1, 2"
instead. Such a recovering logic is defined in Annex B.The
u
flag disables the recovering logic Annex B defined. As a result, you can find errors early. This is similar to the strict mode.
Therefore, the u
flag lets us work better with regular expressions.
Rule Details
This rule aims to enforce the use of u
flag on regular expressions.
Examples of incorrect code for this rule:
/*eslint require-unicode-regexp: error */
const a = /aaa/
const b = /bbb/gi
const c = new RegExp("ccc")
const d = new RegExp("ddd", "gi")
Examples of correct code for this rule:
/*eslint require-unicode-regexp: error */
const a = /aaa/u
const b = /bbb/giu
const c = new RegExp("ccc", "u")
const d = new RegExp("ddd", "giu")
// This rule ignores RegExp calls if the flags could not be evaluated to a static value.
function f(flags) {
return new RegExp("eee", flags)
}
When Not To Use It
If you donโt want to notify regular expressions with no u
flag, then itโs safe to disable this rule.
Version
This rule was introduced in ESLint v5.3.0.