A function is a very important language element in JavaScript and provides a function keyword and a built-in object function, and the following are the possible uses and relationships between them.
Use method One:
Copy Code code as follows:
var foo01 = function ()//or Fun01 = function ()
{
var temp = 100;
This.temp = 200;
return temp + this.temp;
}
Alert (typeof (FOO01));
Alert (foo01 ());
Run Result:
function
300 the most common function usage, set a JavaScript function. The two kinds of writing show the same effect, the only one is that the latter is a higher initialization priority. In a variable scope within a large expansion number, this refers to the owner of the Foo01, the Window object.
Use Method Two:
Copy Code code as follows:
var foo02 = new function ()
{
var temp = 100;
This.temp = 200;
return temp + this.temp;
}
Alert (typeof (Foo02));
Alert (Foo02.constructor ());
Run Result: Object
300 This is a comparison of the use of puzzle function, as if to set a function. But this is actually a user-defined object in JavaScript, but this is an anonymous class. This usage has nothing to do with the use of the function itself, which constructs a variable scope in the large extension, this refers to the scope itself.
Use method Three:
Copy Code code as follows:
var Foo3 = new Function (' var temp = This.temp =; return temp + this.temp; ');
Alert (typeof (Foo3));
Alert (Foo3 ());
Run Result: function
300 Use the System built-in function object to construct a function, which is identical to the first in method one in terms of both effect and initialization precedence, that is, the function body is given in string form.
Use method Four:
Copy Code code as follows:
var Foo4 = Function (' var temp = This.temp =; return temp + this.temp; ');
Alert (typeof (Foo4));
Alert (Foo4 ());
Run Result:
function
300 This method is not commonly used, the effect and method of the same, but it is not clear that there is no new to generate any side effects, which also embodies the largest feature of javascript: Flexible! Can save the province.
On the question of function initialization precedence, see the reply to "the difference between two implementations of the JS class definition prototype method."
