Determine whether a JavaScript object has a specified property.
Syntax
bool
JS_HasProperty(JSContext *cx, JS::HandleObject obj, const char *name,
bool *foundp);
bool
JS_HasUCProperty(JSContext *cx, JS::HandleObject obj,
const char16_t *name, size_t namelen,
bool *vp);
bool
JS_HasPropertyById(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
bool *foundp); // Added in SpiderMonkey 1.8.1
| Name | Type | Description |
|---|---|---|
cx |
JSContext * |
A context. Requires request. In a JS_THREADSAFE build, the caller must be in a request on this JSContext. |
obj |
JS::HandleObject |
Object to search on for the property. |
name or id |
const char * or const char16_t or |
Name of the property to look up. |
namelen |
size_t |
(only in JS_HasUCProperty) The length of name in characters, or -1 to indicate that name is null-terminated. |
foundp |
bool * |
Non-null pointer to a variable of type bool. On success, JS_HasProperty stores true in this variable if obj has a property with the given name, and false if not. |
Description
JS_HasProperty searches an object, obj, and its prototype chain, for a property with the specified name. It behaves like the JavaScript expression name in obj. JS_HasUCProperty is the corresponding Unicode API. JS_HasPropertyById is the same but takes a JS::HandleId for the property name.
If the property exists, this function sets *foundp to true and returns true.
If the object obj has no such property, the function sets *foundp to false and returns true (to indicate that no error occurred).
If an error occurs during the search, the function returns false, and the value of *foundp is undefined.