JS_SetOptions

Obsolete since JSAPI 27
This feature is obsolete.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.

Enables and disables options on a JSContext, replacing all previously set options.

Syntax

uint32
JS_SetOptions(JSContext *cx, uint32 options);

Name	Type	Description
`cx`	`JSContext *`	A context on which to set options.
`options`	`uint32`	The new set of options. This is the logical OR of zero or more flags described below.

Description

JS_SetOptions sets the option flags of a given JS context cx. This function returns a uint32 value containing the previous values of the flags.

To turn individual options on or off, use JS_SetOptions with JS_GetOptions:

// turn on warnings for dubious practices
JS_SetOptions(cx, JS_GetOptions(cx) | JSOPTION_EXTRA_WARNINGS);

// turn off those extra warnings
JS_SetOptions(cx, JS_GetOptions(cx) & ~JSOPTION_EXTRA_WARNINGS);

The options parameter and the return value are the logical OR of zero or more constants from the following table:

Option	Description
`JSOPTION_EXTRA_WARNINGS`	Warn on dubious practice. MXR ID Search for `JSOPTION_EXTRA_WARNINGS`
`JSOPTION_WERROR`	Convert warnings to errors. MXR ID Search for `JSOPTION_WERROR`
`JSOPTION_VAROBJFIX`	Make `JS_EvaluateScript()` use the last object on its `obj` param's scope chain (that is, the global object) as the ECMA "variables object". This flag is recommended. Without it, the two scripts "`x = 1`" and "`var x = 1`", where no variable `x` is in scope, do two different things. The former creates a property on the global object. The latter creates a property on `obj`. With this flag, both create a global property. MXR ID Search for `JSOPTION_VAROBJFIX`
`JSOPTION_PRIVATE_IS_NSISUPPORTS`	Mozilla extension. The context's private data points to an XPCOM object (see `nsISupports`). This is only meaningful if SpiderMonkey is built with XPConnect. MXR ID Search for `JSOPTION_PRIVATE_IS_NSISUPPORTS`
`JSOPTION_COMPILE_N_GO`	Caller of `JS_CompileScript` et al promises to execute the compiled script once only, in the same scope object used for compilation. The caller may not modify objects on the scope chain between compilation and execution. This enables compile-time scope chain resolution of `const`s (a performance optimization). MXR ID Search for `JSOPTION_COMPILE_N_GO`
`JSOPTION_ATLINE`	`//@line number ["filename"]` option supported for the XUL preprocessor and kindred beasts. MXR ID Search for `JSOPTION_ATLINE`
`JSOPTION_XML`	Obsolete since JSAPI 15 ECMAScript for XML (E4X) support: parse `<!-- -->` as a token, not backward compatible with the comment-hiding hack used in HTML script tags. MXR ID Search for `JSOPTION_XML`
`JSOPTION_ALLOW_XML`	Added in SpiderMonkey 15 If this is off, E4X syntax isn't supported no matter what version number is set. MXR ID Search for `JSOPTION_ALLOW_XML`
`JSOPTION_MOAR_XML`	Added in SpiderMonkey 15 ECMAScript for XML (E4X) support: parse `<!-- -->` as a token, not backward compatible with the comment-hiding hack used in HTML script tags. Only used if `JSOPTION_ALLOW_XML` is set. MXR ID Search for `JSOPTION_MOAR_XML`
`JSOPTION_NATIVE_BRANCH_CALLBACK`	The branch callback set by `JS_SetBranchCallback` may be called with a null `script` parameter, by native code that loops intensively. MXR ID Search for `JSOPTION_NATIVE_BRANCH_CALLBACK`
`JSOPTION_DONT_REPORT_UNCAUGHT`	When returning from the outermost API call, prevent uncaught exceptions from being converted to error reports. MXR ID Search for `JSOPTION_DONT_REPORT_UNCAUGHT`
`JSOPTION_RELIMIT`	Added in SpiderMonkey 1.8 Throw an exception if a regular expression backtracks more than n³ times, where n is the length of the input string. MXR ID Search for `JSOPTION_RELIMIT`
`JSOPTION_ANONFUNFIX`	Added in SpiderMonkey 1.8 Disallow `function () {}` in statement context, per ECMA-262 Edition 3. This behavior is the default in releases where this option has been removed. MXR ID Search for `JSOPTION_ANONFUNFIX`
`JSOPTION_JIT`	Obsolete since JSAPI 11 Added in SpiderMonkey 1.8.1 Enables the JIT compilation of code in the context. Note that you may currently (Jan 2009) experience bugs with this option enabled. MXR ID Search for `JSOPTION_JIT`
`JSOPTION_NO_SCRIPT_RVAL`	Added in SpiderMonkey 1.8.1 By setting this option, the application promises to the compiler that a null rval out-param will be passed to each call to `JS_ExecuteScript`. MXR ID Search for `JSOPTION_NO_SCRIPT_RVAL`
`JSOPTION_UNROOTED_GLOBAL`	Added in SpiderMonkey 1.8.1 Instructs the garbage collector not to consider the context's global object a root. The application must ensure that the global object survives as long as the `JSContext`. MXR ID Search for `JSOPTION_UNROOTED_GLOBAL`

Syntax

Description

See Also