typeof
typeof (undefined) without error
undefined object Number boolean function String return value is a string type
false
0 , false , "", undefined, null , NaN
addition of those six are true
null == undefined true
null === undefined false
parseInt（）
parseInt (String, radix) String parsing of the first character for numbers, continue to resolve, not a NaN is returned
parseInt ( '1c3cc4cblllll') returns 1
this
1, pre-compile-time function, this === "" window
2, in the global scope, == this "" window
3, Call and apply to change this point
4, object.function == this "" Who calls the function Object methods inside this ,, who executed if the execution method empty, for the window
as long as no use obj.xxx (), are equivalent to otherwise empty execution, this == "" window
arguments
Test function () {
the console.log (The arguments.callee) // reference point function itself
}
recursive, represents a function
var sum = (function (n){
if(n == 1 )
{
return 1;
}
return n * (arguments.callee)(n-1);
}(5));