MDN may have intermittent access issues April 18 13:00 - April 19 01:00 UTC. See whistlepig.mozilla.org for all notifications.

mozilla
Your Search Results

    JS_IsConstructing_PossiblyWithGivenThisObject

    This article is in need of a technical review.

    Obsolete since JSAPI 17
    This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

    This article covers features introduced in SpiderMonkey 1.8.5

    Determine if a special this object was supplied to the constructor.

    Syntax

    static JSBool
    JS_IsConstructing_PossiblyWithGivenThisObject(JSContext *cx, const jsval *vp,
                                                  JSObject **maybeThis);
    
    Name Type Description
    cx JSContext * The context. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext.
    vp const jsval *  
    maybeThis JSObject **  

    Description

    In the case of a constructor called from JS_ConstructObject and JS_InitClass where the class has the JSCLASS_CONSTRUCT_PROTOTYPE flag set, SpiderMonkey passes the constructor a non-standard this object. In such cases, the following example would provide the additional information of whether a special this was supplied.

    JSBool foo_native(JSContext *cx, uintN argc, jsval *vp) {
      JSObject *maybeThis;
      if (JS_IsConstructing_PossiblyWithGivenThisObject(cx, vp, &maybeThis)) {
        // native called as a constructor
        if (maybeThis)
        // native called as a constructor with maybeThis as 'this'
      } else {
        // native called as function, maybeThis is still uninitialized
      }
    }
    
    Note: A SpiderMonkey embedding does not need to use this query unless the embedding uses JS_ConstructObject(), JS_InitClass() and JSCLASS_CONSTRUCT_PROTOTYPE as described above.

    See Also

    Document Tags and Contributors

    Contributors to this page: Sheppy, luke@mozilla.com, arai, markg, kscarfone
    Last updated by: arai,
    Hide Sidebar