2) The .<script> tag can be written inside the head body or outside the HTML.
3). Using an external file introduction: First create a new JS file demo.js remember: the suffix of all external javascript files. js
<! DOCTYPE html>
3.javascript common input and output mode
1). Alert ("hello!") pop-up window output.
2). Confirm ("Are you sure you're a man?") ) to return a Boolean value by selecting the Pop-up window.
3). Prompt ("Please enter:"); Enter pop-up window
4.Javascript Data Types JavaScript is a weak language and is used to determine what type
String,number,boolean,array,object,null
1). How to see what type of variable you have, using the TypeOf keyword. For objects such as arrays, typeof only Displays object
If you want to determine if it is an array, use alert (as instanceof array); The result is true for the array type.
2). Undefined undefined type, indicating that you have not initialized or used this variable. The undefined type is false.
3). Special note: In JS except Nan, undefined,0 these three numbers are false, the rest are true.
You can tell if a variable has a value assigned. If the assignment is true no assignment is undefined is false;
5. Conversions of data types
1). Convert numbers to Strings
The number is converted to a string Var a=456; Alert (typeof a); A=a.tostring ();//a=456+ ""; Alert (typeof a);
2). Convert strings to Numbers
var b= "one"; alert (b+1); alert (number (b) +1);
3). Note: If you cast a non-numeric value to number, you will get a Nan value;
Using parseint, you can convert several numbers that begin with a string to int, and if the start is not a number, you will only get Nan.
such as Var b= "12px";
Alert (parseint (b)); You can get 12 to change the font size and so on.
Objects of 6.Javascript
Create a Person object function person (name,age) {this.name=name;this.age=age;this.address= "Chengdu, Sichuan";//If you do not use this declaration, This variable is just a local variable, not a property of a class. var m=10;//creation Method This.say=function () {alert (this.name+ "," +this.age);}} Instantiate an object var p1=new person ("Zhang Fei", "P1.name"), Alert (p1.name+ "," +p1.address "alert (p1[" name "]+", "+p1[" address "]); You can also use alert (typeof p1); Get Objectalert (P1 instanceof person); Get True//In the case of JS, for the object, you can get the properties of the object through for-in, which can be used to see what properties are in the frame. For (Var A in P1) {alert (a);//alert (A + ":" +p1[a]);} Another way to define a function: var x=function () {alert ("X")}//at this point x is a function
7. Date Objects
var d=new date ();d Ocument.write (d.getfullyear () + "year" + (D.getmonth () +1) + "month" +d.getdate () + "Day" + "Week" +d.getday ())
8. String
var str1=new String ("abc"), var str2= "abc"; alert (STR1==STR2); The result is true without Equalsvar s=str2.concat ("Hello", "World");
9. Arrays
1).
var as=new Array (); As.push (one); As.push (12);
2).
var mycars=new Array (); mycars[0]= "Saab"; mycars[1]= "Volvo"; mycars[2]= "BMW";
3).
var as=new Array (11,12,13,14,15,222, "15");
4).
var as=["11", 12,1,2];
10.with function
With (document) {//This time all the code in curly braces is based on document as the root object, when using Write (XXX) is equal to document.write (XXX); write (); write (); write (); Write ();//Use alert is also allowed for alert ("ABC");}
11. Event Handling
<! Doctype html>
Javascript Basic Knowledge Collation