Javascript中的函数中的this值

             1 <script>
 2var url="fang.com";
 3var obj={
 4         url:"soufun.com",
 5         func:function(){
 6returnthis.url;
 7        }
 8    };
 910    console.log((obj.func)());
11     console.log((1&&obj.func)())
12 </script>

10.1.7 This
There is a this value associated with every active execution context. The this value depends on the caller and the type of code being executed and is determined when control enters the execution context. The this value associated with an execution context is immutable.

10.2 Entering An Execution Context
Every function and constructor call enters a new execution context, even if a function is calling itself recursively. Every return exits an execution context. A thrown exception, if not caught, may also exit one or more execution contexts.

When control enters an execution context, the scope chain is created and initialised, variable instantiation is performed, and the this value is determined.

The initialisation of the scope chain, variable instantiation, and the determination of the this value depend on the type of code being entered.

10.2.1 Global Code
The scope chain is created and initialised to contain the global object and no others.
Variable instantiation is performed using the global object as the variable object and using property attributes { DontDelete }.
The this value is the global object.

10.2.2 Eval Code
When control enters an execution context for eval code, the previous active execution context, referred to as the calling context, is used to determine the scope chain, the variable object, and the this value. If there is no calling context, then initialising the scope chain, variable instantiation, and determination of the this value are performed just as for global code.

The scope chain is initialised to contain the same objects, in the same order, as the calling context‘s scope chain. This includes objects added to the calling context‘s scope chain by with statements and catch clauses.
Variable instantiation is performed using the calling context‘s variable object and using empty property attributes.
The this value is the same as the this value of the calling context.

10.2.3 Function Code
The scope chain is initialised to contain the activation object followed by the objects in the scope chain stored in the [[Scope]] property of the Function object.
Variable instantiation is performed using the activation object as the variable object and using property attributes { DontDelete }.
The caller provides the this value. If the this value provided by the caller is not an object (note that null is not an object), then the this value is the global object.