JS

来源：互联网发布：js向上取整编辑：程序博客网时间：2024/05/19 22:24

Js基础知识
Js比较好用的框架jQuery(jquery.com)、Dojo(dojotoolkit.org)

Js重要关键字使用
delete in for..in..
number转为string
(5).toString()、String(5)
// number to string
toString()
toString(2)
toString(8)
toString(16)
toFixed(n)
toExponential(n)// 以指数表示法表示数值,n表示小数点后面有几位数字
toPrecision(n)// 用n位有效数字表示数值,在必要的情况下用指数表示
// string to number
Number(<str>)
parseInt // 会忽略数字字符后面的非数字字符
parseFloat // 会忽略数字字符后面的非数字字符

创建数组
var myArray = new Array();
方式一：
myArray[0] = "name";
myArray[1] = 21;
方式二：
["name",100,true];

JS中Array对象定义许多方法
concat: //合并数组
join: //将所有数组元素连接成字符串，以指定分隔符分开
pop: //将数组当成栈使用，删除并返回数组最后一个元素
push： //将数组当成栈使用，并将指定数据添加到数组中
reverse： //就地反转数组元素次序
shift: //类似pop，但是操作的是数组的第一个元素
slice(start, end)://返回一个字数组
sort: //对数组元素排序
unshift //类似于push，但是新元素会被插到数组的开头位置
异常错误处理
try{} catch(e){}finally{}
e(error):
message //对错误条件的说明
name //错误名称
number //错误代号
undefined和null区别
undefined:未赋值或者试图读取对象没有的属性得到的值
null:
undefined == null// true
undefined === null// false

js调试工具：
firebug //可设置断点,探查错误,逐条执行脚本

案例一：
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>Html5</title>
</head>
<body>
<script type="text/javascript">
document.writeln("Hello<br>");
function fun() {
document.writeln("Hello world<br>");
}
fun();
</script>
<script type="text/javascript">
function funJack(name, weather) {
document.writeln("Hello " + name + ", It is " + weather + " today.<br>");
}
funJack("jack", "sunny")
</script>
<script type="text/javascript">
function funReturn(name) {
return "Hello " + name + ".<br>"
}
document.writeln(funReturn("jack"));
</script>
<script type="text/javascript">

function objfun() {
// var obj = new Object();
// obj.name = "jack";
// obj.age = 24;
var obj = {
name:"jack",
age:23
};
return obj;
}
var oo = objfun();
document.writeln("name = " + oo.name + " age = " + oo.age + "<br>");
</script>
<script type="text/javascript">
function objtest() {
return {
name:"tom",
age:20,
printMessage: function() {
document.writeln("name=" + this.name + "<br>");
document.writeln("age=" + this.age + "<br>");
}
};
}
objtest().printMessage();
</script>
</body>
</html>

案例二：
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>HTML5</title>
</head>
<body>
<script type="text/javascript">
var myData = {
name:"tom",
age:11
};
document.writeln("name = " + myData.name + "; age = " + myData.age + "<br>");
myData.name = "jack";
document.writeln("name = " + myData.name + "; age = " + myData.age + "<br>");
myData["name"] = "change";
document.writeln("name = " + myData.name + "; age = " + myData.age + "<br>");
</script>
<hr>
<script type="text/javascript">
var objData = {
name:"join",
weather:"sunny",
printMessage:function(){
document.writeln("name=" + this.name + ",weather=" + this.weather + "<br>")
}
};
objData.hello = "hello world";
objData.sayHello = function () {
document.writeln("say Hello world");
};
for(var prop in objData) {
document.writeln(prop + ":" + objData[prop] + "<br>");
}
document.writeln("<hr>");
delete objData.hello;
delete objData.sayHello;
if (!("hello" in objData)) {
document.writeln("hello attribute is delete<br>");
}
if ("name" in objData) {
document.writeln("name attribute is exist<br>");
}
document.writeln("<hr>");
</script>
</body>
</html>

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