JavaScript anonymous function Summary __ function

Previous blog about JavaScript anonymous functions: http://blog.csdn.net/wusuopuBUPT/article/details/14522631

first, enumerate several common ways to declare JavaScript functions:

Function Demo () {
    //Functions body part
}

It is the essence of the function of the principal assignment to the demo variable, the function of the main body is:

function () {
    //Functions body part
}

So the demo () function can also be defined as this:

var demo=function () {
    //function body part
}

You can call a function like this:

Demo ();

The function of the parentheses is to execute the function body (code block) that the demo variable points to.

Without parentheses, the body of the function is only a piece of text, a string of strings that will not be executed.

Give me a chestnut:

<script>
	var total = 1;
	var demo = function () {Total
		= ten;
		return total;
	}
	
	Alert (demo); Output function Body
	alert (total);//1
	Alert (demo ());//alert (total
	);
</script>

Anonymous Functions

An anonymous function, which can be understood to have a function defined, but does not assign it to a variable.

The definition is as follows:

function ([parameters]) {
    statements;
    [return expression;]
}

Call to anonymous function:

The anonymous function does not have a function name and does not have a variable that points to it, and cannot be invoked anywhere, like a named function, which must be executed immediately after the definition.

As mentioned above, the function of the parentheses is to execute the code block as a function and to pass the arguments within the parentheses, so the anonymous function can be invoked and executed using parentheses:

(function ([parameters]) {
    //function body part
}) ([parameters]);

The first parenthesis encloses the function body, and the second parenthesis executes the function body, [parameters] is the list of arguments to pass.


Example 1:

(function () {
    alert ("anonymous function");
}) ();

Example 2:

(function (x,y) {
    alert (x+y);
}) (1,2);

Note: End with semicolon "; ", it's not a code block, it's called a function."

Example 3: Computes the value of 1+2+3+...+99+100 with an anonymous function.

<script language= "JavaScript" type= "Text/javascript" >
(Function (m,n) {
    var total=0;
    if (m>=n) {
        alert ("value range is not correct. ");
        return false;
    }
    for (Var i=m;i<=n;i++) {
        total+=i
    }
    Alert (total);
}) (1,100);
</script>

Save and execute code, pop-up warning box, show 5050, anonymous function executed successfully.


Example 4: anonymous function with return value。

<script language= "JavaScript" type= "Text/javascript" >
alert (
    function (m,n) {
        var total=0;
        if (m>=n) {
            alert ("value range is not correct. ");
            return false;
        }
        for (Var i=m;i<=n;i++) {
            total+=i
        }
        return total;
    }) (1,100)  Do not add a semicolon here
);
</script>

Save and execute the code with the same result as in Example 3.


Summary: The function name is a reference to the body of the function (the code block), which is performed as a function of the code block.

Reference: http://www.itxueyuan.org/view/6314.html