JS_EvaluateScript

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本文详细介绍了SpiderMonkey中JS_EvaluateScript及JS_EvaluateUCScript函数的使用方法。这两个函数用于在指定的作用域中编译并执行JavaScript脚本。文章解释了函数参数的意义，包括上下文、作用域、源代码字符串等，并说明了如何处理错误。

https://developer.mozilla.org/en-US/docs/SpiderMonkey/JSAPI_Reference/JS_EvaluateScript

JS_EvaluateScript

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Compile and execute a script.

Syntax

JSBool JS_EvaluateScript(JSContext *cx, JSObject *obj,
    const char *src, uintN length, const char *filename,
    uintN lineno, jsval *rval);

JSBool JS_EvaluateUCScript(JSContext *cx, JSObject *obj,
    const jschar *src, uintN length, const char *filename,
    uintN lineno, jsval *rval);

Name	Type	Description
`cx`	`JSContext *`	The context in which to run the script. Requires request. In a `JS_THREADSAFE` build, the caller must be in a request on this `JSContext`.
`obj`	`JSObject *`	The scope in which to execute the script. This parameter is documented in detail at `JS_ExecuteScript`.
`src`	`const char ` or`const jschar `	String containing the script to compile and execute.
`length`	`uintN`	The length of `src`, in characters.
`filename`	`const char *`	Name of file or URL containing the script. Used to report filename or URL in error messages.
`lineno`	`uintN`	Line number. Used to report the offending line in the file or URL if an error occurs.
`rval`	`jsval *`	Out parameter. On success, if `rval` is not `NULL`, `*rval` receives the result value.

Description

JS_EvaluateScript compiles and executes a script in the specified scope, obj. JS_EvaluateUCScript is the Unicode version of the function.

src is the string containing the text of the script. length indicates the size of the text version of the script in characters.

filename is the name of the file (or URL) containing the script. This information is used in messages if an error occurs during compilation. Similarly, lineno is used to report the line number of the script or file where an error occurred during compilation.

rval is an optional out parameter. If it is non-null, then on success, the result value is stored in *rval. This value is determined the same way as for the standard evalfunction. In the common case where the script is just an expression, the result value is simply the value of that expression. More generally, the result value is the value of the last-executed expression statement in the script that isn't in a function.

If a script compiles and executes successfully, JS_EvaluateScript or JS_EvaluateUCScript stores the result in *rval, if non-null, and returns JS_TRUE. Otherwise it returns JS_FALSE and the value left in *rval is undefined.