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intro to JavaScript.js
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intro to JavaScript.js
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//Javascript
//where to put scripts
<html>
<head>
<script defer src = 'example.js'></script>
</head>
<body>
</body>
</html>
-----undefined variable
var message;
alert(message == undefined); //true
-------test whether a variable has value
if (car != null){
//operations
}
------NaN(not a number)
isNaN(10) //false
isNaN('blue') //true
------string to number
Number()
pasrseInt('22.34', 10) //22 , based on 10
parseFloat('22.34') //22.34
-------string methods
var text = 'This is a test string';
alert(test.length);
--------convert to string
String(object)
--------operator
++num;
--num;
var age = 29;
var anotherage = --age + 2;
alert(age); //28
alert(anotherage); //30
var num1 = 2;
var num2 = 20;
var num3 = --num1 + num2; //21
var num4 = num1 + num2 //21
num++;
num--;
var num1 = 2;
var num2 = 20;
var num3 = num1-- + num2; //22
var num4 = num1 + num2; //21
----logic operation
! negative
&& and
|| or
-----conditional operator
var max = (num1 > num2) ? num1: num2;
if (condition) statement1 else statement2
do {
//
} while ();
while (){
//
}
for (var i = 0; i < count; i++){
//
}
for (; i < count; ){
//same as while expression
}
with(){
//operations upon a single object
}
switch (i) {
case value:
//do sth
break;
case value2;
//do sth
break;
default:
//do sth
}
------User input
text = prompt('Enter some text:')
------DOM
window.document.write
window.alert
document.URL
document.title
document.referrer //last visited url
document.lastModified //last modify date
document.cookie
document.links // list of links in document
document.links[2].href
window.history.go(-2) // go back to the second last website
window.history.back() //last
window.histroy.forward() //next
window.location.href = "http://www.google.com" //load google into the current window
window.location.reload //refresh the website
------Array-------
//create an array
scores = new Array(1,3,5,7) //one way
scores = [1,3,5,7] //the other way
scores.length
scores.sort()
var test = "this is a very long string!"
parts = test.split(" ")
total = parts.join(" ")
----Object-------
//initiation functon
function Card(name, address, work, home){
this.name = name;
this.address= address;
this.work = work;
this.home = home;
this.printCard = PrintCard; //method
}
function PrintCard(){
document.write(this.name, this.address, this.work, this.home);
}
Tom = new Card("tom", '123 West', '222222', '3434343');
//Adding method to exiting object
String.prototype.heading = addhead;
function addhead(level) {
html = 'h' + level;
text = this.toString();
return html + text;
}
------Built-in functions
Math.random()
-------defining event reaction in javaScript file
function mousealert(){
alert('warning!');
}
document.onmousedown = mousealert;
//in html define and id
<a href = "" id = 'link1'>
//in javascript
obj = document.getElementById("link1");
obj.onclick = MyFunction;
----event project is what users type on keyboard
<body onKeyPress = "getkey(event);">
//in JavaScript
function getkey(e){
if (!e) e = window.event;
}
-----event object for mouse action
onMouseOver
onMouseOut
onclick
//<a href = "http://www.google.com" onClick = "return(window.confirm('Sure?'));"></a>
onDblClick
onMouseDown
onMouseUp
---Javascript to detect mouse status
function mousestatus(e){
if (!e) e = window.event;
button = e.button;
whichone = (button < 2)? "left": "right";
message = e.type + ":" + whichone + "\n";
document.form1.info.value += message;
}
obj = document.getElementById('testlink');
obj.onmousedown = mousestatus;
obj.onmouseup = mousestatus;
obj.onclick = mousestatus;
obj.ondblclick = mousestatus;
---open new page
winObj = window.open("URL", "windowname", "feature list");
winObj.close();
---adjust window
window.moveTo()
window.moveBy();
window.resizeTo();
window.resizeBy();
------overTime
window.setTimeout