Home > Developer > Web Develop
<! DOCTYPE html>
<meta charset= "UTF-8" >
<title></title>
<body>
<script type= "Text/javascript" >
function box (num1,num2) {
return num1+num2; General function Declaration method
}
alert (box);
var box=function (num1,num2) {
return num1+num2; Using variable initialization functions
}
alert (box);
var box=new Function (' num1 ', ' num2 ', ' return num1+num2 ');
alert (box); Use the constructor of new to declare
Functions can pass functions
The following example is common, not passed as a function, but passed as the return value of the function.
function box (sum,num) {
return sum+num;
}
function sum (num) {
return num+10;
}
var result=box (sum (10), 10); SUM (10) The return value of the function is passed here, as is the normal variable, no difference
alert (result);//30
To pass the function itself as a parameter, not the result of the function
function box (sum,num) {
return sum (num);
}
function sum (num) {
return num+10;
}
var result=box (sum,10);//This sum is a function that is passed as a parameter to another function instead of the return value of the function.
alert (return);//20
function box (num) {
if (num<=1) {
return 1;
}else{
Return Num*arguments.callee (num-1);//4*3*2*1=24 factorial, recursive
}//Use callee to invoke itself to implement recursion
}
Alert (Box (4));
var color= "Red"; Here, color is the global variable, and this variable is the property of the window.
var box={
Color: "Blue",
Saycolor:function () {
alert (This.color); The color here is the Box property, which is the local variable
Here this, we are determined to represent the box object
}
}
alert (This.color); Red.
Box.saycolor (); Blue.
function box (name,age) {
return name+age;
}
alert (box.length);
function box (num1,num2) {
return num1+num2;
}
Method one: function sum (num1,num2) {//apply and call can impersonate another function
Return box.apply (this,[num1,num2]);//this represents the window scope, "" means the parameter passed
}
Method Two: function sum (num1,num2) {
Return box.apply (this,arguments);//This can be passed as an array
}
Alert (Box (10,10)); 20
Alert (sum (10,10)); 20
function box (num1,num2) {
return num1+num2;
}
function sum (num1,num2) {
Return Box.call (this,num1,num2);//call only pass parameters, others are the same as apply
}
Alert (sum (10,10));
var color= "Red";
var box={
Color: ' Blue '
}
function Saycolor () {
alert (This.color);
}
Saycolor (); Global
Use call is to implement the object impersonating, impersonating box, impersonating window under
Saycolor.call (window); Posing as window red
Saycolor.call (box); Impersonating box, the scope is inside the box object, so color is blue
</script>
</body>
JS function declaration
Start building with 50+ products and up to 12 months usage for Elastic Compute Service
1 on 1 presale consultation
24/7 Technical Support 6 Free Tickets per Quarter Faster Response
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.
A comprehensive suite of global cloud computing services to power your business
Payment Methods We Support
