-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathvariable.html
90 lines (84 loc) · 2.63 KB
/
variable.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>变量定义</title>
</head>
<body>
<button>press me</button>
<script>
//变量声明,定义没有赋值，是undefined变量,没有定义，则是not defined
var myName;
//变量初始化
myName='Thomas';
//变量声明同时赋值
var button = document.querySelector('button');
button.onclick=function(){
var name= prompt('what is your name');
if (name === 'tom'){
alert('hello old friend');
}else {
alert('hello '+name);
}
};
//变量类型
var myAge=17;//Number
var city='shanghai';//Strings
var iAmAlive=true;//Boolean
var myNameArray = ['chris','bob','jim'];//arrays
var myNumArray=[10,15,40];
var dog = {name:'Spot',breed:'Al'};//object
console.log(dog.name);
//数组里面的每一项可以是不同的类型
var random=['tree',795,[1,2,3]];
//Loose type
var myNumber='500';
console.log(typeof(myNumber));
myNumber=500;
console.log(typeof(myNumber));
//number和string类型转换
var myDate='19'+'67';
console.log('myDate type:'+typeof(myDate));
var myString='123';
var myNum=Number(myString);//如果myString不是数字，Number函数返回NaN，可以使用isNaN来判断
console.log('myNum type:'+typeof(myNum));
var myString2=myNum.toString();
console.log('myString2 type:'+typeof(myString2));
//数组的操作
var sequence=[0,1,2,3,4,5,6,7];
//使用length属性返回数组长度
console.log("len of sequence is "+sequence.length);
//轮询数组
for(var i=0;i<sequence.length;i++){
console.log(sequence[i]);
}
//字符串和数组之间的相互转换
var myData = 'Manchester,London,Liverpool,Birmingham,Leeds,Carlisle';
var myArray = myData.split(',');
console.log("length of myArray :"+myArray.length+",myArray[0]="+myArray[0]);
var myNewString = myArray.join(',');
console.log('myNewString:'+myNewString);
//使用push(),pop()在数组后面添加／移除 item
myArray.push('Cardiff');
console.log(myArray);
var item=myArray.pop();
console.log(myArray);
console.log("remove "+item);
//使用unshift,shift在数组头部插入/移除 item
myArray.unshift('Edinburgh');
console.log(myArray);
var removedItem=myArray.shift();
console.log(myArray);
console.log("remove "+removedItem);
//得到某一个item的index
var pos = myArray.indexOf('Liverpool');
console.log('pos='+pos);
//删除指定位置
myArray.splice(pos,1);
console.log(myArray);
//拷贝数组
var myArrayCopy=myArray.slice();
console.log(myArrayCopy);
</script>
</body>
</html>