JavaScript must have basic knowledge

1. JavaScript is a lightweight scripting language for browser parsing.

2, HTML, JSP and other internal JS code written in between <script></script>, external JS file to write JS code can not have <script></script>, because the reference to external JS, The JS code is referenced to the <script></script>,

Referenced by <script src= "./myscript.js" ></script> (referencing an external JS file, read from the WebContent folder by default, if an older item might read from Webroot)

3, JavaScript data display common way:

Window.alert ();//Browser hint box, window can omit

Console.log ();//write content to the console, often used for debugging, you can see the structure of the data

document.write ();//write content to the browser page

Innerhtml= "Add content between tags";

4, JS comments (single-line and multiline comments are the same as Java, JS and Java the same point is case-sensitive, ignoring the space, so it is indented; the variables start with a letter, not recommended by $ and _)

Single-line Comment

/* * * Multi-line Comment

5. Common Ways to select objects

document.getElementById ("myID");//element

Document.getelementsbyname ("name");//nodelist

document.getElementsByTagName ("Input");//nodelist

6. JS Type

8 Common data types: string number Boolean array object null (NULL, empty variable) undefined (the default value when the variable is assigned) function

Common 3 types of objects: Date Array Object

7, commonly used JS event

OnLoad//Browser page has finished loading

OnClick//Click events

Change//value changed, commonly used in drop-down list

onmouseover//mouse in an HTML tag

onmouseout//mouse to move out of an HTML tag

onkeydown//user presses the mouse button

8. Special characters in strings

such as: var str = "Double quotes inside double quotes" KDFJKDFJ "This is not correct"//all change to single quotation marks is not correct

Correct: var str = "Double quotation mark inside quotes \" Kdfjkdfj\ "This is not a good notation."

var str = "Double quotation mark ' KDFJKDFJ ' is not written"//internal use single quotation marks

9, fold the line with the backslash

Eg:document.write ("content before wrapping \

Post-line content ");//For a line of too long, wrapping, the backslash is resolved to a space

Ten typeof and Instanceof

var type = type of "AAA";//Displays the data type to which a variable belongs

var arr = [1, 2, 3, 4];

if (arr instanceof Array) {//Displays the object type to which an object variable belongs

document.write ("Arr belongs to array type");

}

10. Type Conversion

Other turn strings use ToString ();

String to value, Number (str),//parseint (str);p arsefloat (str);

Automatic type conversion:

document.write ("5" + null);//5null

document.write (5 + null);//5

document.write ("5" + 1);//51

document.write ("5"-1);//4

11, JS is expression

For example: var regExp = modifier of/e/i;//i regular expression, case-insensitive;/e/Regular expression body

Two methods:

Regexp.test (str);//true/flase;

Regexp.exec (str);//matches a lookup in STR, returns null if not found; returns the first

12. Form Verification

<form name= "Testform" action= "a.html" method= "POST" onsubmit= "return MyFunction ()" >

Testform<input type= "text" name= "name"/>

<input type= "Submit" value= "Submission"

</form>

Get forms: Document.forms[testform][name].value;

Add ID, get it with ID.

13. JSON

Json.parse (JSONSTR);//Convert JSON object to JS object

Json.stringify (jsobject);//Convert JS object to JSON object

14, javascript:void (0);//void (expression), the expression executes, the result is not received, so there is no response

The difference between href= "#" and href= "javascript:void (0)"
# contains a location information, the default anchor is #top is the top of the page.

and javascript:void (0), only represents a dead link.

When the page is long, it uses # to locate the page in the format: # + ID.

If you want to define a dead link please use Javascript:void (0).

15. Dom

<div id= "Div1" >
<p id= "P1" > This is a paragraph. </p>
<p id= "P2" > this is another paragraph. </p>
</div>

<script>
var para=document.createelement ("P");
var Node=document.createtextnode ("This is a new paragraph. ");
Para.appendchild (node);

var Element=document.getelementbyid ("Div1");
Element.appendchild (para);
</script>

Reference or reference in this article: Beginner's Tutorial

Http://www.runoob.com/js/js-tutorial.html

JavaScript must have basic knowledge