深入arguments

arguments對象的內部實現原理：ECMA中的描述：10.1.8 Arguments ObjectWhen control enters an execution context for function code, an arguments object is created and initialised as follows:The value of the internal [[Prototype]] property of the arguments object is the original Object prototype object, the one that is the initial value of Object.prototype (see 15.2.3.1).A property is created with name callee and property attributes { DontEnum }. The initial value of this property is the Function object being executed. This allows anonymous functions to be recursive.A property is created with name length and property attributes { DontEnum }. The initial value of this property is the number of actual parameter values supplied by the caller.For each non-negative integer, arg, less than the value of the length property, a property is created with name ToString(arg) and property attributes { DontEnum }. The initial value of this property is the value of the corresponding actual parameter supplied by the caller. The first actual parameter value corresponds to arg = 0, the second to arg = 1, and so on. In the case when arg is less than the number of formal parameters for the Function object, this property shares its value with the corresponding property of the activation object. This means that changing this property changes the corresponding property of the activation object and vice versa.<script>//demo01:(function (a,b){arguments[1]=2;var b=3;alert(arguments[1]);//2})(1);//demo02:(function (a,b){arguments[1]=2;alert(b);//undefined})(1);//demo03:(function (a,b){arguments[0]=2;var a=3;alert(arguments[0]);//3})(1);//demo04:(function (a){arguments[0]=2;var a=4;alert(arguments[0]);//4})(1);//demo05:(function (a){console.log(arguments);//[1]Array.prototype.splice.call(arguments,0,1);console.log(arguments);//[]alert(a+"---"+arguments[0]);//1---undefined})(1);//demo06:(function (a){var arr = Array.prototype.splice.call(arguments,0,1);alert(a+"---"+arr[0]);//1---undefined})(1);</script>