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    JS_HasInstance

    This article is in need of a technical review.

    JSAPI method equivalent to the instanceof operator in JavaScript.

    Syntax

    bool
    JS_HasInstance(JSContext *cx, JS::Handle<JSObject*> obj, JS::Handle<JS::Value> v, bool *bp);
    
    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.
    obj JS::Handle<JSObject*> Constructor/prototype to test.
    v JS::Handle<JS::Value> The value to test.
    bp bool * Out parameter. On success, *bp receives the result of the test.

    Description

    JS_HasInstance determines if a specified JS value, v, is an instance of JS object, obj. This function is equivalent to v instanceof obj test in JavaScript. On success, JS_HasInstance stores the result of the instanceof test in *bp and returns true. On error or exception, it returns false, and the value left in *bp is undefined.

    When providing a prototype as obj, the prototype's JSClass must have its hasInstance method set. Otherwise JS_HasInstance returns false.

    See Also

    Document Tags and Contributors

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