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JS DeleteProperty

Removes a specified property from an object.


JSBool JS_DeleteProperty(JSContext *cx, JSObject *obj, const char *name);

JSBool JS_DeletePropertyById(JSContext *cx, JSObject *obj, jsid id); 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 JSObject * Object from which to delete a property.
name or id const char * or jsid Name of the property to delete.


JS_DeleteProperty removes a specified property, name, from an object, obj. JS_DeletePropertyById is the same but takes a jsid for the property name. These functions are identical to JS_DeleteProperty2 and JS_DeletePropertyById2 except that they do not have an out parameter.

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 obj's JSClass.delProperty hook is called. No property is deleted, but this is not an error.
  • If obj has the specified property but it is permanent, nothing happens. 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, obj's JSClass.delProperty hook is called. If the hook returns JS_FALSE, the error is propagated. Otherwise, if obj is sealed, an error is raised. Otherwise, the property is removed.

These functions return JS_TRUE on success, regardless of whether a property was actually deleted, and JS_FALSE on error or exception.

(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.)

Internally, property deletion is implemented by the JSObjectOps.deleteProperty callback.

To remove all properties from an object, call JS_ClearScope.

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Last updated by: Jorend,