Javascript中同名标识符优先级

function fn(fn){
	alert(fn);
}
fn('hello'); // --> "hello"

function fn(a){
	var a;
	alert(a);
}
fn('hello'); // --> "hello"

function fn(a){
	var a = 1;
	alert(a);
}
fn('hello'); // --> "1"

function fn(a){
	var a = a;
	alert(a);
}
fn('hello');

10.5  Declaration Binding Instantiation
Every execution context has an associated VariableEnvironment. Variables and functions declared in ECMAScript code evaluated in an execution context are added as bindings in that VariableEnvironment’s Environment Record. For function code, parameters are also added as bindings to that Environment Record.
Which Environment Record is used to bind a declaration and its kind depends upon the type of ECMAScript code executed by the execution context, but the remainder of the behaviour is generic. On entering an execution context, bindings are created in the VariableEnvironment as follows using the caller provided code and, if it is function code, argument List args: // 设args为实参数组

1.  Let env be the environment record component of the running execution context’s VariableEnvironment.
2.  If code is eval code, then let configurableBindings be true else let configurableBindings be false.
3.  If code is strict mode code, then let strict be true else let strict be false.
4.  If code is function code, then 
a.  Let func be the function whose [[Call]] internal method initiated execution of code. Let names be the value of func’s [[FormalParameters]] internal property.   // 设func为函数，names为形参数组
b.  Let argCount be the number of elements in args. // 设argCount为实参个数
c.  Let n be the number 0. // 设n为0
d.  For each String argName in names, in list order do // 顺序遍历形参数组，对每个形参名argName作处理
i.  Let n be the current value of n plus 1. // n=n+1 (即n为当前形参序号，从1开始)
ii.  If n is greater than argCount, let v be undefined otherwise let v be the value of the n’th element of args. // 如果n大于形参数目，则设v为undefined。否则v为对应的实参值
iii.  Let argAlreadyDeclared be the result of calling env’s HasBinding concrete method passing argName as the argument. // 设argAlreadyDeclared为[当前环境.标识符是否已声明(argName)]的返回值
iv.  If argAlreadyDeclared is false, call env’s CreateMutableBinding concrete method passing argName as the argument. // 如果为false，即未声明，则创建之
v.  Call env’s SetMutableBinding concrete method passing argName, v, and strict as the arguments. // 设置环境中的argName变量值为v
5.  For each FunctionDeclaration f in code, in source text order do // 对于函数声明，按代码先后作处理（对于函数声明详细信息，见附2）
a.  Let fn be the Identifier in FunctionDeclaration f.
b.  Let fo be the result of instantiating FunctionDeclaration f as described in Clause 13.
c.  Let funcAlreadyDeclared be the result of calling env’s HasBinding concrete method passing fn as the argument.
d.  If funcAlreadyDeclared is false, call env’s CreateMutableBinding concrete method passing fn and configurableBindings as the arguments. // 如果标识符未声明，则声明之
e.  Call env’s SetMutableBinding concrete method passing fn, fo, and strict as the arguments. // 设置值
6.  Let argumentsAlreadyDeclared be the result of calling env’s HasBinding concrete method passing "arguments" as the argument  // 设argumentsAlreadyDeclared为[当前环境.标识符是否已声明("arguments")]的返回值
7.  If code is function code and argumentsAlreadyDeclared is false, then // 如果未声明，则处理
a.  Let argsObj be the result of calling the abstract operation CreateArgumentsObject (10.6) passing  func, names, args, env and strict as arguments.
b.  If strict is true, then 
i.  Call env’s CreateImmutableBinding concrete method passing the String "arguments" as the argument.
ii.  Call env’s InitializeImmutableBinding concrete method passing "arguments" and argsObj as arguments.
c.  Else,
i.  Call env’s CreateMutableBinding concrete method passing the String "arguments" as the argument.
ii.  Call env’s SetMutableBinding concrete method passing "arguments", argsObj, and false as arguments.
8.  For each VariableDeclaration and VariableDeclarationNoIn d in code, in source text order do // 按代码顺序处理变量声明
a.  Let dn be the Identifier in d.
b.  Let varAlreadyDeclared be the result of calling env’s HasBinding concrete method passing dn as the argument.
c.  If varAlreadyDeclared is false, then // 如果未声明
i.  Call env’s CreateMutableBinding concrete method passing dn and configurableBindings as the arguments. // 声明标识
ii.  Call env’s SetMutableBinding concrete method passing dn, undefined, and strict as the arguments. // 设值为undefined

 fn();  

 function fn(){  
     var a = 1;  
     var a;
     alert(a);
 }

函数声明(FunctionDeclaration)的分辨请见：http://www.iteye.com/topic/802482#1741032
(不知道是谁投的隐藏帖，无语了)

此外clue对ECMAScript的理解太认同，比如忽视了最基本的JS中“解释期”，“运行期”。将两者混为谈。
显然他没有理解执行上下文栈(execution context stack)，执行上下文(execution context)，变量对象(variable object)，激活对象(activation object)等。
而是引用一大段ECMAScript 10.5节 去表达自己对ECMAScript的学习和理解。

赞楼主。楼主把各种情况下同名标识符优先级一一列出，说明楼主很有心，关注细节。解疑了困惑我很久的问题。但结尾应该把所有讨论情况总结下。应该是这样的：

局部变量(vars) > 形式参数(formal parameter) > arguments
                                            > 函数名