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    JS_DeleteProperty2

    This article is in need of a technical review.

    Removes a specified property from an object.

    Syntax

    bool
    JS_DeleteProperty2(JSContext *cx, JS::HandleObject obj, const char *name,
                       bool *succeeded);
    
    bool
    JS_DeleteUCProperty2(JSContext *cx, JS::HandleObject obj, const char16_t *name, size_t namelen,
                         bool *succeeded);
    
    bool
    JS_DeletePropertyById2(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
                           bool *succeeded); // Added in SpiderMonkey 1.8.1
    
    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::HandleObject Object from which to delete a property.
    name or id const char * or const char16_t or JS::HandleId Name of the property to delete.
    namelen size_t (only in JS_DeleteUCProperty2) The length of name in characters; or -1 to indicate that name is null-terminated.
    succeeded bool * Out parameter. On success, *succeeded receives false if the property was not deleted because it is permanent and true otherwise.

    Description

    JS_DeleteProperty2 removes a specified property, name, from an object, obj, and stores true or false in *succeeded. It behaves like the JavaScript expression delete obj[name]. JS_DeleteUCProperty2 is the Unicode version of the function. JS_DeletePropertyById2 is the same but takes a JS::HandleId for the property name.

    First, a property lookup is performed. Then one of the following cases applies:

    • If obj has no property with the given name or id, or if obj inherits the specified property from its prototype, then *succeeded is set to true and obj's JSClass.delProperty hook is called (which may change *succeeded). No property is deleted, but this is not an error.
    • If obj has the specified property but it is permanent, then *succeeded receives false. No property is deleted, but this is not an error.
    • Otherwise obj has a non-permanent own property with the given name or id. In this case, *succeeded is set to true and obj's JSClass.delProperty hook is called (which may change *succeeded). If the hook returns false, the error is propagated. Otherwise, if obj is not configurable, an error is raised. Otherwise, *succeeded receives true and the property is removed.

    These functions return true on success, regardless of whether a property was actually deleted. On error or exception, the return value is false, and the value left in *succeeded is unspecified.

    JSObjectOps.deleteProperty implements this behavior.

    (In JavaScript 1.2 and earlier, attempting to delete a permanent property caused an error. There is no longer any way to get this behavior.)

    To remove all properties from an object, call JS_ClearScope.

    See Also

    Document Tags and Contributors

    Contributors to this page: MMondor, Dria, fscholz, Jorend, arai
    Last updated by: arai,
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