SpiderMonkey JSAPI

JSAPI

The JSAPI is the C API for the SpiderMonkey JavaScript engine.

JS::Value / jsval

namespace JS { class Value; }
typedef JS::Value jsval;

• Contain JavaScript values of any type

  • number

  • string

  • boolean

  • reference to object

    • Object

    • Array

    • Date

    • Function

    • null

    • undefined

• JS::Value and jsval are the same type, jsval is the old name

JSClass

A JSClass acts as a vtable for JS objects that allows JSAPI clients to control various aspects of the behavior of an object like property lookup.

struct JSClass {
    const char          *name;
    uint32_t            flags;

    // Mandatory function pointer members.
    JSPropertyOp        addProperty;
    JSDeletePropertyOp  delProperty;
    JSPropertyOp        getProperty;
    JSStrictPropertyOp  setProperty;
    JSEnumerateOp       enumerate;
    JSResolveOp         resolve;
    JSConvertOp         convert;

    // Optional members (may be null).
    JSFinalizeOp        finalize;
    JSCheckAccessOp     checkAccess;
    JSNative            call;
    JSHasInstanceOp     hasInstance;
    JSNative            construct;
    JSTraceOp           trace;

    void                *reserved[42];
};

JSObject

class JSObject : public js::gc::Cell {/*...*/};

• The type of JavaScript objects in the JSAPI.

prototype

Most objects have a prototype. ( JS_GetPrototype )

• An object inherits properties, including methods, from its prototype.

parent

Most objects have a parent. ( JS_GetParent )

own properties

A property of an object that is not inherited from its prototype.

Almost every object can have any number of its own properties.

Each property has a name, a getter, a setter, and property attributes. ( JS_GetPropertyAttributes )

Most properties also have a stored value.

Stored value

The stored value of an object property is its last known value.

• JS_DefineProperty allows the application to specify a property's initial stored value.

• JS_LookupProperty fetches a property's stored value without triggering its getter.

JSClass

Every object is associated with aJSClass.

JSString

Represents a primitive JavaScript string in the JSAPI.

An array of char16_t characters and a length.

JSNative

typedef bool
(* JSNative)(JSContext *cx, unsigned argc, JS::Value *vp);

The type of many JSAPI callbacks.

Each JSNative has the same signature, regardless of what arguments it expects to receive from JavaScript.