Subj : Help clarifying the concept of scope in spidermonkey
To   : netscape.public.mozilla.jseng
From : J.P.
Date : Fri Jul 09 2004 01:38 pm

In the code below, I create two JSObjects (obj1 and oj2), for two scope. 
They are using the same context. I run script "x=0;x=x+1;" in obj1, then 
run "x=x+1" in obj2. I expected that x equal to 1 in obj1 and getting an 
error in obj2, since obj1 and obj2 are seperated scopes and x is not 
defined in obj2.

But the actual result is
Scope 1: x=1
Scope 2: x=2

So the question is: Why doesn't obj2 have its own x, but use the x in obj1?

To make the code do what I intend to do, I have to call 
JS_ClearScope(js_context, obj1) after done using obj1.

////////////////////////////////////////////////////
JSRuntime * js_runtime = JS_NewRuntime(1024L * 1024L);
JSContext * js_context = JS_NewContext(js_runtime, 8192);
JSClass scope_class = {
	"clsScope", 0,
	JS_PropertyStub, JS_PropertyStub,
	JS_PropertyStub, JS_PropertyStub,
	JS_EnumerateStub, JS_ResolveStub,
	JS_ConvertStub, JS_FinalizeStub
	};

//scope 1
JSObject *obj1 = JS_NewObject(js_context, &scope_class, NULL, NULL);
std::string s;
JS_InitStandardClasses(js_context, obj1);
jsval val;
s = "x=0; x=x+1;";
JS_EvaluateScript(js_context, obj1, s.c_str(), s.length(), NULL, 0, &val);
int i = JSVAL_TO_INT(val);
std::cout << "Scope 1: x=" << i << std::endl;

//scope 2
JSObject *obj2 = JS_NewObject(js_context, &scope_class, NULL, NULL);
JS_InitStandardClasses(js_context, obj2);
s = "x=x+1;";
JS_EvaluateScript(js_context, obj2, s.c_str(), s.length(), NULL, 0, &val);
i = JSVAL_TO_INT(val);
std::cout << "Scope 2: x=" << i << std::endl;
JS_DestroyContext(js_context);
JS_DestroyRuntime(js_runtime);
JS_ShutDown();
///////////////////////////////////////////////////////////

.