时间：2022-06-07 09:22:34 | 栏目：Python代码 | 点击：次
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>js的引入方式</title>
</head>
<body>
<!-- js的第一种引入方式 -->
<!-- <script>
alert("js的第一种引入方式")
</script> -->
<!-- js的第二种引入方式 -->
<!-- <script src="myjs.js"></script> -->
<!-- js的第三种引入方式 -->
<!-- onclick单击事件 -->
<div onclick="alert(11)" >点我1</div>
<!-- js的第四种引入方式 -->
<a href="javascript:alert('你点我了么?')">点我2</a>
</body>
</html>
小提示：
js三大对象 1. 本地对象：js语法 2. bom对象：浏览器相关的成员（针对于浏览器的控制）brower object model 3. dom文档对象：关于html文件节点相关的数据、相关的值（针对于html的控制） document object model js是单线程的异步程序 定时器是单线程的异步程序（例子）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>注释/变量</title>
</head>
<body>
<script>
// ###1 注释分为两类: (1) 单行注释 (2) 多行注释
// 我是单行注释
/* 我是多行注释 */
// ###2 变量
/* var的用作是划分当前变量的作用域 不写var,默认声明全局的变量 */
var a = 1;
var a=1,b=2,c=3
console.log(a);
console.log(b,c)
// ###3 变量的命名
var $ = "特殊的变量名";
var $abc = 111;
console.log($);
console.log($abc);
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>数据类型</title>
</head>
<body>
<script>
/*
数据类型: 分为两大类 (基本数据类型 + 引用数据类型)
基本数据类型: Boolean , Number , String , undefined , null
引用数据类型: Object(Array , function , Date ... )
*/
// ###1. Boolean 布尔类型
var a1 = true;
var a1 = false;
console.log( a1 , typeof(a1) )
// ###2. Number 数字类型
var num = 0b101;
var num = 0o127;
var num = 0xff;
var num = 1000;
var num = 3.13;
var num = 3.13e2;
// Infinity 无穷大
var num = 3.13e999999999999999999999999999999999999;
// -Infinity 负无穷大
var num = -3.13e999999999999999999999999999999999999;
console.log(num , typeof(num) )
// NaN => not a number 不是一个数字
/*
1.NaN和任何数字计算都是NaN
2.与NaN做比较,除了NaN!=NaN为真,剩下都是false
*/
var num = 10 - "abc";
var num = NaN + 1
var num = NaN == NaN
var num = NaN != NaN; // true
var num = NaN > 100; // false
var num = isNaN(NaN); // true
console.log(num , typeof(num))
// ###3.String 字符串类型
// 单引号''
var string = 'I love js';
// 双引号""
var string = "i love python very much";
// 在转义字符前面加\,防止转义原型化输出
var string = "我爱你,\\n 中国"
console.log(string)
// 反引号`` 1.支持跨行 2.解析变量
// 1.支持跨行
var string = `
<ul>
<li>111</li>
</ul>
`
// 2.解析变量 ${变量名}
var name = "赵沈阳";
var string = `${name}`;
console.log(string , typeof(string))
// ###4.Object 对象类型
// 1.定义一个空对象
var obj = new Object()
var obj = {}
console.log(obj,typeof(obj))
// 2.js对象(字典格式)
var obj = {"a":1,"b":2}
console.log(obj , typeof(obj))
// 3.js对象,可以在类外添加成员
obj.name = "张三";
console.log(obj , typeof(obj));
// 4.js对象(数组格式)
var arr = new Array();
var arr = [];
arr[0] = 10;
arr[1] = 11;
arr[2] = 12;
var arr = [10,11,12,13];
console.log(arr , typeof(obj));
// ###5 function 函数类型(归属于object)
function func(){
console.log("我是函数");
}
func()
console.log(func,typeof(func))
// ###6 undefined 未定义类型
var a;
console.log(a , typeof(a))
// 注意: null 可以理解成关键字 (等价于python中None)
var a = null
console.log(a , typeof(a))
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>强制转换 - Number</title>
</head>
<body>
<script>
// 1. parseInt 强制转换成整型
/* 要求: 必须数字开头; */
var num = 1.934567; //1
var num = "abc"; //NaN
var num = "123"; //123
var num = "123abc"; //123
var num = "abc123"; //NaN
var num = "1.34abc" //1
var num = [] //NaN
var num = false //NaN
var res = parseInt(num);
console.log(res ,typeof(res))
// 2.parseFloat 强制转换成浮点型
/* 要求: 必须数字开头; */
var num = 100; //1
var num = "abc"; //NaN
var num = "123"; //123
var num = "123abc"; //123
var num = "abc123"; //NaN
var num = "1.34abc"; //1.34
var num = {}; //NaN
var num = true;
var res = parseFloat(num);
console.log(res ,typeof(res))
// 3.Number类型强转
/* 要求:必须是存纯数字或者布尔类型*/
var a = false
var a = "123.456"; //123
var res = Number(a)
console.log(res ,typeof(res))
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>强制转换 - String</title>
</head>
<body>
<script>
/*
字符串的强转是在原有类型的两边套上引号,表达字符串类型;
*/
var a = 100;
var a = 4.89;
var a = "abc";
var a = [];
var a = undefined;
var a = null;
var a = NaN;
var res = String(a);
console.log(res , typeof(res))
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>强制转换 - Boolean</title>
</head>
<body>
<script>
/*
//布尔类型为假的七中情况:
0 0.0 '' NaN undefined null false
*/
var a = false;
var a = null;
var a = 0;
var a = 0.0;
var a = '';
var a = NaN;
var a = undefined;
// 注意点 空数组 空对象都是true
var a = []; // true
var a = {}; // true
var res = Boolean(a);
console.log(res , typeof(res));
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>自动类型转换 Number Boolean String 三者之间的转换</title>
</head>
<body>
<script>
// 1.Number+Boolean
var res = 10 + true;
var res = 3.4 + true;
var res = 10 + 3.1;
console.log(res ,typeof(res))
// 2.Number+Boolean+String (对于字符串来说 +号意味着拼接)
var res = true + "100";
var res = 100 + "101" + 100;
console.log(res,typeof(res))
// 3.除了+号,剩下的都可以做运算(必须是数值)
var res = 100 - "101";
var res = 100 - "99abc";
console.log(res,typeof(res))
</script>
</body>
</html>
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>js中的运算符</title></head><body> <script> // (1) ++ -- 递增,递减 // num++ 先赋值在自增 var num = 100; var res = num++; console.log(res , typeof(res)); var res = num++; console.log(res , typeof(res)); // num++ 先自增在赋值 var num = 100; var res = ++num; var res = ++num; console.log(res , typeof(res)); // (2) === !== (全等于,不全等于)比较两样东西1.比较值的大小 2.比较值的类型 var res = "1" == 1; console.log(res , typeof(res)); var res = "1" === 1; var res = "1" !== 1; console.log(res , typeof(res)); // (3) && => and , || => or , ! => not var num = 8 if(num > 5 && num <10){ console.log("ok1~"); } if(num>10 || num < 3){ console.log("ok2~"); } var num = 0 if(!num){ console.log("ok3~"); } // (4) 三元(目)运算符 [ js: 表达式?真值:假值 ] [ python :res = 正确 if 条件表达式 else 错误 ] var age = 18; var res = age >= 18 ? "成年人":"儿童"; console.log(res) </script></body></html><!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>js中的运算符</title>
</head>
<body>
<script>
// (1) ++ -- 递增,递减
// num++ 先赋值在自增
var num = 100;
var res = num++;
console.log(res , typeof(res));
var res = num++;
console.log(res , typeof(res));
// num++ 先自增在赋值
var num = 100;
var res = ++num;
var res = ++num;
console.log(res , typeof(res));
// (2) === !== (全等于,不全等于)比较两样东西1.比较值的大小 2.比较值的类型
var res = "1" == 1;
console.log(res , typeof(res));
var res = "1" === 1;
var res = "1" !== 1;
console.log(res , typeof(res));
// (3) && => and , || => or , ! => not
var num = 8
if(num > 5 && num <10){
console.log("ok1~");
}
if(num>10 || num < 3){
console.log("ok2~");
}
var num = 0
if(!num){
console.log("ok3~");
}
// (4) 三元(目)运算符 [ js: 表达式?真值:假值 ] [ python :res = 正确 if 条件表达式 else 错误 ]
var age = 18;
var res = age >= 18 ? "成年人":"儿童";
console.log(res)
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>流程控制 -> 分支结构 </title>
</head>
<body>
<script>
var mashengni = "美女";
//1.单项分支
// if(mashengni == "美女"){
// alert("给他买好吃的~");
// }
//2.双项分支
// if(mashengni == "野兽"){
// alert("给他一榔头~");
// }else{
// alert("跳起来给他一榔头~");
// }
//3.多项分支
// 不推荐判断条件连续比较,有可能失效;
var salary = 1000;
if(10000 < salary && salary < 12000){
console.log("正常薪资范围~");
}else if(12000 <= salary && salary < 15000){
console.log("超过一般水平~");
}else if(15000 <= salary && salary <18000){
console.log("大神级毕业生~");
}else if(salary >= 18000){
console.log("王牌毕业生~");
}else{
console.log("回炉重生~")
}
//4.巢状分支
var youqian = true;
var youfang = true;
if(youqian){
if(youfang){
console.log("老子要嫁给你~!");
}
}
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>分支结构 : switch case </title>
</head>
<body>
<script>
var date = new Date();
console.log(date);
// 获取星期 getDay
var week = date.getDay();
console.log(week)
week = "1"
// 注意点: switch case中的判断(全等于): (1) 值的比较(2)类型的比较 全部符合才能满足条件;
switch (week){
case 1:
console.log('星期一');
break;
case 2:
console.log('星期二');
break;
case 3:
console.log('星期三');
break;
case 4:
console.log('星期四');
break;
case 5:
console.log('星期五');
break;
case 6:
console.log('星期六');
break;
default:
console.log("星期日!");
break;
}
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>分支结构 : 循环结构 </title>
</head>
<body>
<script>
// ### 1.for循环
/*
语法特征:
1号 2号 3号
for(初始值;判断条件;自增自减的值){
code1
code2..
}
先执行1,2满足后执行代码体
然后执行3,2满足后在执行代码体
以此类推...
直到不满足条件终止循环;
*/
// 打印 1~100
for(var i = 1;i<=100;i++){
console.log(i);
}
// 打印1~100 遇到50,自动跳过;
for(var i = 1;i<=100;i++){
if(i == 50){
continue;
}
console.log(i);
}
// ### 2.while 循环
//遇到5,终止循环
i = 0
while(i<10){
if( i == 5){
break;
}
console.log(i);
i++;
}
console.log("<===============第一组===================>")
// ### 3.for( var i in Iterable ) 获取的是数组中的索引号;
var arr = ["孟浩然","赵子龙","康乃馨","张飞","汪精卫"];
for(var i in arr ){
console.log(i);
console.log(arr[i]);
}
console.log("<===============第二组===================>")
// 获取的是js对象中的键
var dic = {"a":"王同培","b":"马村你","c":"张宇"};
for(var i in dic){
console.log(i)
console.log(dic[i]) ;
}
console.log("<===============第三组===================>")
// ### 4.for( var i of Iterable ) 获取的是数组中的值; [等价于python中 for i in Iterable:]
for(var i of arr){
console.log(i);
}
console.log("<===============第四组===================>")
// 注意点: for(var i of dic) 不能遍历js对象[字典] error
/*
var dic = {"a":"王同培","b":"马村你","c":"张宇"};
for(var i of dic){
console.log(i)
}
*/
// 字符串的遍历:
for(var i of "abcdefg"){
console.log(i)
}
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>函数</title>
</head>
<body>
<script>
func1()
// ###1 函数
// 方式一 普通函数 (存在预加载机制,提前把函数加载到内存中,然后代码整体在执行)
func1()
function func1(){
console.log(111);
}
// 方式二 匿名函数(匿名函数没有预加载价值,必须先定义在调用)
// func2() error
var func2 = function(){
console.log('我是func2~');
}
func2();
// 方式三 不推荐 (了解)
// var func3 = new Function("alert('我是func3~');alert('woshi3333');");
// console.log(func3,typeof(func3));
// func3();
// var func4 = new Function("x","y","alert(x+y)");
// func4(5,6);
// 方式四 闭包函数
function func5(){
var a = 100;
function func6(){
console.log(a,"<===>");
return "我是闭包函数";
}
return func6;
}
func = func5();
res = func();
console.log(res);
// 方式五 箭头函数
function mysum(x,y){
return x+y;
}
res = mysum(5,6)
console.log(res,"<=======11122233=======>");
var mysum = (x,y) => {return x+y;}
var res = mysum(5,6);
console.log(res,"========3334444=========");
// ###2 函数参数 (普通位置参数,默认参数)
// js中的形参实参不匹配不会报错
function func7(a,b,c=3){
console.log(a,b,c);
}
func7(10,11);
func7(10,11,12);
func7(10,11,12,13);
console.log("<==============================>")
// arguments 自动收集所有的实参
// 计算任意个数值的累加和;
function func8() {
// console.log(a,b)
// console.log(arguments)
var total = 0;
for(var i of arguments){
total += i;
console.log(i);
}
return total;
}
res = func8(1,100,2,3,4,5,56,6);
console.log(res);
</script>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>函数的调用</title>
</head>
<body>
<script>
function func(){
console.log("函数正在执行 ... ");
}
// 1.正常调用
func();
// 2.函数的立即执行
(function func2(){
console.log("函数正在执行2 ... ")
})();
// 3.匿名函数的立即执行
(function(){
console.log("匿名函数正在执行3 ... ")
})();
// 4.其他立即执行的方法;
!function(){
console.log("我在执行4 ... ");
}();
~function(){
console.log("我在执行5 ... ");
}();
</script>
</body>
</html>