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This article covers features introduced in SpiderMonkey 17

Test whether the given string is a valid ECMAScript identifier.


JS_IsIdentifier(JSContext *cx, JS::HandleString str, bool *isIdentifier);

JS_IsIdentifier(const char16_t *chars, size_t length); // Added in SpiderMonkey 38
Name Type Description
cx JSContext * Pointer to a JS context from which to derive runtime information. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext.
str JS::HandleString The string to test.
chars const char16_t * The pointer of the string to test.
length size_t The length of chars.
isIdentifier bool * Out parameter. On success, *isIdentifier receives whether str is an identifier or not.


JS_IsIdentifier tests if the given string is a valid ECMAScript identifier. On successful, JS_IsIdentifier stores the test result to *isIdentifier and returns true, otherwise returns false and the value of *isIdentifier is undefined.

JS_IsIdentifier which takes chars and length is infallible, so just returns whether the chars are an identifier.

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 Contributors to this page: kscarfone, arai
 Last updated by: kscarfone,