Obsolete since JSAPI 52
This feature is obsolete.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.


Get or specify the error reporting mechanism for an application.


JS_GetErrorReporter(JSRuntime *rt);

JS_SetErrorReporter(JSRuntime *rt, JSErrorReporter er);
Name Type Description
cx JSRuntime * Pointer to a JS runtime whose errors should be reported via your function. 
er JSErrorReporter The user-defined error reporting function to use in your application, described below.

Callback Syntax

typedef void
(* JSErrorReporter)(JSContext *cx, const char *message, JSErrorReport *report);
Name Type Description
cx JSContext * The context in which the error happened.
message const char * An error message.
report JSErrorReport * An error report record containing additional details about the error.


JS_SetErrorReporter enables you to define and use your own error reporting mechanism in your applications. The reporter you define is automatically passed a JSErrorReport structure when an error occurs and has been parsed by JS_ReportError. JS_SetErrorReporter

JS_GetErrorReporter returns the value set by JS_SetErrorReporter.

Typically, the error reporting mechanism you define should log the error where appropriate (such as to a log file), and display an error to the user of your application. The error you log and display can make use of the information passed about the error condition in the JSErrorReport structure.

The error reporter callback must not reenter the JSAPI. Like all other SpiderMonkey callbacks, the error reporter callback must not throw a C++ exception.

Note that JS_SetErrorReporter has no facility to directly pass a user data pointer to the error reporting function. You can work around this by using the JS_SetRuntimePrivate and JS_GetRuntimePrivate methods. Example code with error handling omitted:

    class MyRequest {

      void execute() {
        auto rt = JS_NewRuntime(memlimit);
        JS_SetRuntimePrivate(rt, this);
        JS_SetErrorReporter(rt, &MyRequest::dispatchError);
        // execute JS

      void onError(const std::string& error) {
        // handle error

      static void dispatchError(
          JSContext* ctx,
          const char* message,
          JSErrorReport* report) {
        auto rt = JS_GetRuntime(ctx);
        auto rt_userdata = JS_GetRuntimePrivate(rt);
        if (rt_userdata) {
          auto req = static_cast<MyRequest*>(rt_userdata);



See Also