javascript colon usage instructions_javascript tips

It kept popping up in front of my eyes, so I searched online and looked up information. I was very depressed that there were not many posts on the Internet explaining the use of colon, and they were fragmented and not in-depth enough. After reading them, I became even more confused. After two days of struggling, I finally got the hang of colon ( :) With a better understanding, I hope it will be helpful to those who want to understand the usage of colon.
1. Switch statement branch
2. ?:false of ternary expression
3. Declare members of object literals
4. Declare labels

1 and 2 Believe in the Earth Everyone knows that, right? If someone doesn’t know, I’ll change it to say that all programmers on earth know it, haha ​​
3. We often use object direct quantities. What are object direct quantities?
Object literals (also called object initializers) are composed of a list. The elements of this list are property/value pairs separated by colons. The elements are separated by commas. The entire list is contained in curly braces. among.
Objects in JavaScript can have properties and methods just like objects in object-oriented languages ​​such as C# and JAVA.
We have many ways to create javascript objects. For example, you can use Object to create,

Copy code The code is as follows:

var obj1 = new Object();
obj1.X = "20px";
obj1.Y = "30px";
obj1.myFunction = function() { alert ("I am a method!"); };
obj1.myFunction();

Create an object using object literals:

Copy code The code is as follows:

var obj2={X:"20px",Y:"30px",myFunction: function(){alert("I am a method!");}}
obj2.myFunction();

Creating objects using object literals seems very simple.
Of course You can also write something similar to the Class class first and then create it using the constructor:

Copy the code The code is as follows:

function myClass(x, y) {
this.X = x;
this.Y = y;
}
myClass.prototype.myFunction=function(){
alert("I am a method!");
}
var obj3 = new myClass("20px", "30px");
obj3.myFunction();

4. Declaration tags
There are many scripting languages. In addition to javascript, we can also use other scripting languages ​​to implement the functions that javascript can achieve;
Example:
< ;input type="button" onclick="vbscript:vbFunction()" value='button'/>
When the button is clicked, vbscript syntax will be used to execute the vbFunction method you defined with vbscript;
If Change vbscript:vbFunction() after onclick to javascript:vbFunction(); and an error will occur.
You can also directly call the method without writing these statements,

At this time, the method in onclick, Whether you use vbscript or javascript, the IE browser will recognize it on its own and use the corresponding syntax to execute it. Of course, other browsers do not support vbscript.
Usually when we use javascript, it is customary to add a statement, that is, "javascript: ",

"javascript:"Often used by those who claim to be hackers People use "javascript:" to bypass some simple or more advanced HTML form restrictions and cookie/session verification; as well as SQL injection. If you want to know more, you can check it elsewhere, but learn not to cause damage. Haha
A simple example:
First open the homepage of Baidu at www.baidu.com, then copy the following sentence directly into the address bar of the browser, press Enter,
javascript:alert (document.forms[0].wd.value='csdn');document.forms[0].submit()
What is the effect? Yes, we used JavaScript to directly manipulate the text in the search box and submit the form. You can study more complex operations by yourself.