常见用途
- HTML DOM 操作(结点操作,比如添加、修改、删除结点)
- 给网页增加动态功能
js 输出与调试
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>输出 hello world</title>
<script type="text/javascript">
//弹框输出
// alert("hello world");
//调试输出 类似 NSLog()
console.log("你好,我是调试输出")
</script>
</head>
<body>
/*页内样式*/
</body>
</html>
image.png
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>JS 基本语法</title>
<script type="text/javascript">
//1.基本语法
var age = 18;//number
var money = 100.88;//number
var name = "jack"//string
var name2 = "rose";//string
var result = true;//boolean
var number = null;//object
var number2 = undefined;//undefined
//2.输出
console.log(age,money,name,name2,result,number,number2);
//3.变量的真实类型 typeof
console.log(typeof age,typeof money,typeof name,typeof name2,typeof result,typeof number,typeof number2);
//4.基本数据类型的运算
//遵循的规律:
// 运算是从左往右.人物类型的变量与 str 类型运算,会被强制转换为 string
//4.1 字符串拼接
var newName = name + name2 + '-';
console.log(newName)
//4.2 题目 v
var str1 = 10 + 10 + '10'//2010
var str2 = '10' + 10 + 10//101010
var str3 = 10 + '10' + 10//101010
//5 数组
var numbers = [-10, 'jam',name,result,number,['hello','hi']];//可以装任何东西
//5.1 遍历数组
for(var i = 0; i<numbers.length; i++){
console.log(numbers[i]);
}
for (var i in numbers) {
console.log(numbers[i]);
}
//5.2JS 中常用的属性
//删除数组中的最后一个元素
numbers.pop();
//从最后插入一个元素
numbers.push('XMF');
//6. JS 蟾宫的类库 Math
var numberArray = [10, 212, 3233, 32];
var maxNum = Math.max(10,20,50,30);
console.log(maxNum);
var newMacNum = Math.max.apply(this,numberArray);
console.log(newMacNum);
</script>
</head>
<body>
</body>
</html>
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