JS基础
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>js文件的引入</title>
<!-- 内部的js -->
<script type="text/javascript">
// 编写js代码
alert('我是mjj');
</script>
<!-- 外部的js -->
<script type="text/javascript" src='js/index.js'></script>
</head>
<body>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>变量</title>
</head>
<body>
<script type="text/javascript">
// 单行注释
/*
多行注释
*/
// 变量初始化
var x = 30;
var X = 30;
// 声明变量
var y;
// 变量赋值
y = 50;
var name = '王聪聪';
/*
1.必须使用字母、下划线（_） $开始
2.多个英文字母 驼峰 myName
3.不能使用js中关键字 和保留字来进行命名
4.严格区别大小写
*/
var _A = 40;
var $ = 90;
// alert(_A);
// alert($ );
// alert(x);
// alert(X);
var z = 40;
z = 50;
alert(z);
</script>
</body>
</html>
<!-- 变量类型 基本的数据类型 Number String Boolean undefined null 引用的数据类型 Object Array Function --> <!DOCTYPE html> <html> <head> <title></title> </head> <body> <script type="text/javascript"> // number数值类型 var a = 3; var b = 1.234; var c = -1; // typeof 来检查当前变量的数据类型 // alert(typeof a); // alert(typeof b); // alert(typeof c); // 字符串 string 'abc234' 或者是 "我是mjj" var name = 'mjj'; var en = "abc"; // alert(typeof name); // alert(typeof en); // boolean 0（假 false） 和1（真 true） var c = 3 <= 4; // alert(c); // alert(typeof c); // 声明变量 var x; // alert(x); // alert(typeof x); // 空对象 var y = null; alert(y); alert(typeof y); </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>运算符-算数运算符</title>
</head>
<body>
<script type="text/javascript">
var x = 10;
var y = 4;
var sum = x + y;
var sum2 = 4 + 5 + x + y;
var en = x-y;
var or = x * y;
var op = x % y * sum;
alert(or);
alert(op);
var c = (x + sum) / 4 -3;
alert(c);
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>递增和递减以及赋值运算符</title>
</head>
<body>
<script type="text/javascript">
// ++
// --
var x = 3;
// x++;
x = x + 1;
// alert(x);
var a = 5;
var b = 6;
a = b;
var c = 10;
// c = c + 5;
c += 5;
c -= 2;
c *= 4;
c /= 3;
alert(c);
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>字符串</title>
</head>
<body>
<script type="text/javascript">
// var str = '@#$%^&*';
// alert(str);
// var word = "hello";
// var newWord = word;
// alert(typeof word);
// alert(newWord);
// var name = 'would you eat a "apple"?';
// alert(name);
// var str = "I 'm "mjj"";
// alert(str);
// var one = 'hello';
// var name = 'mjj';
var joined = 'hello' +' ' + 'mjj';
alert(joined);
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>数字和字符串</title>
</head>
<body>
<script type="text/javascript">
/*
var a = 'mjj' + 521;
alert(a);
alert(typeof a);
*/
/*
var b = '18' + '40';
alert(b);
alert(typeof b);
*/
// 1.隐式转换 数值转字符串
var num = 234;
var myStr = num + "";
// alert(typeof myStr);
// 2.toString() 数值转字符串
var myStr2 = num.toString();
// alert(typeof myStr2);
// 字符串转数值
var myNum = Number(num);
// alert(typeof myNum);
var n = '2424fhfh';
var a = Number(n);
alert(typeof a);//NaN Not a number
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>数组Array</title>
</head>
<body>
<script type="text/javascript">
// 创建
var shopping = ['香蕉','苹果','牛奶','红牛'];
// alert(shopping);
// alert(typeof shopping);
// console.log(shopping);
var rand = ['tree','345',[1,2,3]];
// console.log(rand);
// 访问
var item1 = rand[0];
console.log(item1);
rand[0] = '榴莲';
console.log(rand);
var a = rand[2][2];
console.log(a);
// 访问数组的长度 for
console.log('数组的长度是:' + rand.length);
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>条件判断</title>
</head>
<body>
<script type="text/javascript">
/*
var distance = 10;
var nowDistance = 16;
if ( nowDistance <= distance) {
console.log('自动驾驶');
}else{
console.log('人为驾驶');
}
*/
var weather = 'rainyxxxxxx';
if (weather === 'sunny') {
console.log('天气非常棒,可以出去玩耍');
}else if(weather === 'rainy'){
console.log('天气下雨了,在家里呆着');
}else if(weather === 'snowing'){
console.log('天气下雪了,可以出去滑雪');
}else{
alert('输入的天气有错,重新输入');
}
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>比较运算符</title>
</head>
<body>
<script type="text/javascript">
// === 等同于 和 !==
var a = 5;
var astr = '5';
var isequal1 = a === astr;
console.log(isequal1);
// == 等于 和!= 不等于
var isequal2 = a == astr;
console.log(isequal2);
console.log(4 <= 4);
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>逻辑运算符</title>
</head>
<body>
<script type="text/javascript">
var weather = 'sunny';
var temp = 32;
/*
if (weather === 'sunny') {
if (temp > 30) {
console.log('在家里吹空调,吃西瓜');
}else{
console.log('天气非常好,可以出去玩耍了');
}
}
// && 逻辑与 并且 || 逻辑或 或者 !true
*/
if (weather === 'sunny' && temp > 30) {
console.log('在家里吹空调,吃西瓜');
}else if(weather === 'sunny' && temp <= 30){
console.log('天气非常棒,可以出去玩耍了')
}
// 数学考过80 或者英语考过85 才可以玩游戏
var mathScore = 77;
var enlishScore = 80;
if (mathScore >= 80 || enlishScore >= 85) {
console.log('可以玩游戏');
}else{
console.log('在家里写作业');
}
var isLogin = false;
alert(!isLogin);
if (!isLogin) {
console.log('用户已登录');
}
</script>
</body>
</html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>switch语句</title> </head> <body> <script type="text/javascript"> var weather = 'rainy'; switch (weather) { case 'sunny': alert(1); break; case 'rainy': alert(2); // 编写switch语句 小心break,cash穿透 break; case 'snowing': alert(3); break; default: alert(4); break; } </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>三元运算符</title>
</head>
<body>
<script type="text/javascript">
// if...else
// (条件) ? run this code : run this code;
var isresult = 1 < 2 ? '真的' : '假的';
alert(isresult);
</script>
</body>
</html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>for循环</title> </head> <body> <script type="text/javascript"> // 循环 来做1+2+3....+10000 // 1+2+3+....+10000 /* for(初始化条件;结束条件;递增条件){ //run this code } */ var i; var sum = 0; for(i = 1; i <= 10000;i++){ sum = sum + i; // sum = 1 ,i = 2 // sum = 3, i = 3 // sum = 6, i = 4 } console.log(sum); var shopping = ['香蕉','苹果','牛奶','红牛']; var j; for(j = 0; j < shopping.length; j ++){ // console.log(shopping[j]); var htmlStr = '<h1>'+shopping[j]+'</h1>'; console.log(htmlStr); document.write(htmlStr); } </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>break和continue</title> </head> <body> <script type="text/javascript"> // break 可以跳出当前循环 var x = 0; for(;;){ //死循环 if(x > 100){ break; } x++; } console.log(x); // 1+2+3+4+5+6+7+9+10 var sum = 0; for(var i = 1; i <= 10; i++){ if(i === 8){ // break; // 跳出当前循环,下次循环继续进行 continue; } sum = sum + i; } alert(sum); </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>while循环</title>
</head>
<body>
<script type="text/javascript">
/*
初始化条件
while(判断循环结束条件){
// run this code
递增条件
}
*/
/*
var sum = 0; //计算的和
var n = 99; //初始的奇数
while (n > 0) {
sum = sum + n;
n = n - 2;
}
alert(sum);
*/
// do while
// 1到100之间的数
/*
先判断 再执行
var sum = 0;
var i = 1;
while (i <= 100) {
sum = sum + i;
i ++;
}
alert(sum);
*/
// do-while 先执行一次 再判断
var sum = 0;
var i = 1;
do{
sum = sum + i;
i++;
console.log(sum);
}while(i <= 1);
</script>
</body>
</html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>函数</title> </head> <body> <script type="text/javascript"> // 做饭 // 买菜 // 洗菜 // 切菜 // 炒菜 // 吃菜 // 洗碗 // 睡觉..... // 买菜 // 洗菜 // 切菜 // 炒菜 // 吃菜 // 洗碗 // 睡觉..... // 买菜 // 洗菜 // 切菜 // 炒菜 // 吃菜 // 洗碗 // 睡觉..... // 买菜 // 洗菜 // 切菜 // 炒菜 // 吃菜 // 洗碗 // 睡觉..... // 封装重复性代码 function 做饭(isBad,a,b,c) { //isBad 形式参数 alert(isBad); if(isBad){ alert('点个外卖'); }else{ // 买菜 // 洗菜 // 切菜 // 炒菜 // 吃菜 alert('做饭了'); } } var bad = true; //刀坏了 // 做饭(bad); // 洗碗 // 睡觉..... 做饭(bad); </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>函数返回值和函数表达式</title> </head> <body> <script type="text/javascript"> // addition(加法) subtraction(减法) multiplicatio(乘法) division(除法) function addition(a,b){ var sum = a + b; return sum; } function subtraction(a,b){ return a - b; } function multiplicatio(a,b){ return a * b; } /* function division(a,b){ return a / b; } */ // 函数表达式 var division = function(a,b){ return a / b; } var r = addition(3,2); var r2 = subtraction(3,2); var r3= multiplicatio(3,2); var r4 = division(3,2); console.log(r); console.log(r2); console.log(r3); console.log(r4); </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>函数作用域</title> </head> <body> <!-- <script type="text/javascript"> var a = 1; console.log(a); function add(){ var b = 3; console.log(a); } add(); // console.log(b); </script> --> <script type="text/javascript" src="js/first.js"></script> <script type="text/javascript" src="js/second.js"></script> <script type="text/javascript"> console.log(window); first(); second(); </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>object</title>
</head>
<body>
<script type="text/javascript">
/*
var name = '火腿肠';
function 老虎(){
alert(name);
}
function 企鹅(){
alert(name);
}
老虎();
*/
// 对象 (属性和方法)字面量创建 姓名,年龄,性别 ,爱好(动作)
var person = {
name : 'mjj',
age: 18,
sex:'女',
fav: function(a){
alert('爱好姑娘');
return '姑娘' + a + '岁';
}
}
console.log(person);
console.log(person.name);
console.log(person.fav(18));
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Javascript常用内置对象</title>
</head>
<body>
<script type="text/javascript">
// 字面量创建一样
// var arr = [1,2,3];
// 内置对象 native object 对象 : 属性和方法
// document.write('呵呵呵');
// Array
// js提供构造函数
var colors = new Array();
var colors2 = [];
if (Array.isArray(colors)) {
// 对数组进行操作
colors[0] = 'red';
colors[1] = 'blue';
colors[2] = 'yellow';
var a = colors.toString();
console.log(a);
console.log(typeof a);
console.log(colors);
// console.log(colors[0]);
// console.log(colors.length);
}else{
// .....
}
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>数组常用的方法</title>
</head>
<body>
<script type="text/javascript">
/*
var arr = [1,2,3];
var a = arr.toString();
var b = arr.toLocaleString();
console.log(a);
console.log(b);
var person1 = {
toLocaleString : function(){
return 'mjj';
},
toString: function(){
return '么吉吉';
}
}
var person2 = {
toLocaleString : function(){
return '隔壁老王';
},
toString: function(){
return '隔壁老李';
}
}
var people = [person1,person2];
console.log(people);
console.log(people.toString());
console.log(people.toLocaleString());
*/
// 分割为字符串
var colors = ['red','blue','green'];
var a = colors.join('|');
console.log(a); // red|blue|green
// 栈(lifo last - in- first - out)方法. push() pop() 队列方法
// push() 往数组的最后一项添加内容
var newlength = colors.push('purple');
console.log(newlength);
console.log(colors);
// pop() 从数组末尾删除最后一项
var lastItem = colors.pop();
console.log(lastItem);
console.log(colors);
// 队列 fifo 先进先出 unshift() shift()
newlength = colors.unshift('yellow');
console.log(newlength);
console.log(colors);
var firstItem = colors.shift();
console.log(firstItem);
console.log(colors);
var values = [0,3,2,16,15,10];
// 数组倒序
// values.reverse();
// console.log(values);
// sort() 排序 升序 或者降序
// 对数据排序（示例）
this.allData.sort((a, b) => {
return a.value - b.value // 升序
})
// values.sort();
// console.log(values); //[0, 10, 15, 16, 2, 3]
function compare1(a,b){
/*
// a位于b之前
if (a < b ) {
return -1;
}else if(a > b){
return 1;
}else{
return 0;
}
*/
return a - b;
}
function compare2(a,b){
/*
// a位于b之前
if (a < b ) {
return 1;
}else if(a > b){
return -1;
}else{
return 0;
}
*/
return b - a;
}
// values.sort(compare1); //升序
// console.log(values);
values.sort(compare2);
console.log(values);
// 操作方法 concat() slice() splice()
// 1.concat() 数组合并
var colors = ['red','blue'];
var newColors = colors.concat('green');
newColors = newColors.concat({name:'zhangsan'});
console.log(newColors);
//2.slice() 将当前数组中的一个或者多个项创建一个新数组
var newcolors = colors.concat({name:"lisi"},['black','purple']);
console.log(newcolors); //5
// newcolors = newcolors.slice(1,2);
newcolors = newcolors.slice(-1,-2); //slice(3,4)
console.log(newcolors);
// 3.splice() 删除 插入 替换
// 3.1 删除
var names = ['张三','李四','mjj','alex'];
names.splice(0,2);
console.log(names); // ["mjj", "alex"]
// 3.2 插入
names.splice(1,0,'熊大大','jack');
console.log(names);// ["mjj", "熊大大", "jack", "alex"]
// 3.3 替换
names.splice(1,1,'xiongdada');
console.log(names); // 第二个1代表插入的位置["mjj", "xiongdada", "jack", "alex"]
// 4.位置方法 indexOf() lastIndexOf()
var names = ['张三','mjj','王五','mjj','赵六'];
// alert(names.indexOf('mjj')); //1
// alert(names.lastIndexOf('mjj')); //3
// alert(names.indexOf('mjj',2)); //3
// alert(names.lastIndexOf('mjj',2)); //1
// alert(names.lastIndexOf('mjjxxxx',2)); //如果查不到结果 返回-1
// 5.迭代方法
// 5.1 filter() 将数组的元素进行过滤
var numbers = [1,2,3,6,19,4,20];
var filterResult = numbers.filter(function(item,index,array){
console.log('item:'+ item);
console.log('index:'+ index);
console.log('array:'+ array);
return item > 10
});
console.log(filterResult);
// 5.2 map()方法
var mapresult = numbers.map(function(item,index,array){
return item * 2;
})
console.log(mapresult);
for(var i = 0; i < mapresult.length; i ++){
// console.log(mapresult[i]);
}
// 5.3 forEach()
mapresult.forEach(function(item,index){
console.log(item);
})
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>map方法的应用</title>
</head>
<body>
<script type="text/javascript">
var oldArray = [
{
name:'张三',
age: 17
},
{
name:'mjj',
age: 29
},
{
name:'李四',
age: 30
}
];
/*
var newNames = [];
var newAges = [];
for(var i = 0; i < oldArray.length; i ++){
var myname = oldArray[i].name;
var myage = oldArray[i].age;
newNames.push(myname);
newAges.push(myage);
}
console.log(newNames);
console.log(newAges);
*/
var newNames = oldArray.map(function(item,index){
return item.name
})
var newAges = oldArray.map(function(item,index){
return item.age
})
console.log(newNames);
console.log(newAges);
</script>
</body>
</html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>字符串的常用方法</title> </head> <body> <script type="text/javascript"> // 属性 // length // 方法 /* charAt() charCodeAt() concat() slice() substring() substr() indexOf() lastIndexOf() trim() //常用 toLowerCase() toUpperCase() toLocaleLowerCase() toLocaleUpperCase() */ // var str = 'hello world'; //切片 /* console.log(str.length);//获取字符串的长度 11 console.log(str.charAt(1)); //e 获取指定的字符 console.log(str.charCodeAt(1)) //101 获取指定的字符对应的编码 console.log(str.concat(' mjj',' jack')); //拼接字符串 通常情况 不适用它来做拼接,使用 +来做多个字符的拼接 console.log(str.slice(2)); console.log(str.substring(2)); console.log(str.substr(2)); // 第一个参数是起始的位置,第二个参数是结束的位置 顾头不顾尾 console.log(str.slice(2,4)); console.log(str.substring(2,4)); // 第二个参数是返回的字符数 console.log(str.substr(2,6)); console.log(str.slice(-3,-1)); //rld slice(8,10) console.log(str.slice(8,10)); */ var str = 'hello world'; console.log(str.indexOf('o')); //4 console.log(str.lastIndexOf('o')); //7 console.log(str.indexOf('o',6)); //7 console.log(str.lastIndexOf('o',6)); //4 // trim()清除当前 字符串的前后后格 var str = ' hello world '; console.log(str.trim()); console.log(str); var str = 'Hello Mjj'; // console.log(str.toUpperCase()); console.log(str.toLowerCase()); </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>Document</title> </head> <body> <script> // 对“hello world”进行翻转处理 要求变为："dlorw olleh" function reserve_str() { var alp = 'hello world' var r_alp = alp.split("") // console.log(r_alp) // ['d','l','r','o'..'e','h'] r_alp.reverse() //反转 var r_str = r_alp.join('') //拼接为字符串 return r_str } var s = reserve_str() alert(s) // 'dlrow olleh' </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>查找当前字符e在字符串中的所有位置</title> </head> <body> <script type="text/javascript"> // 查找e 在str中的所有的位置 var str = 'He unfolded the map and set it on the floor.'; var arr = []; var pos = str.indexOf('e'); //1 console.log(pos); while(pos > -1){ // 找到当前e字符对应的位置 arr.push(pos); pos = str.indexOf('e',pos+1); } console.log(arr); </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Date日期对象</title> </head> <body> <script type="text/javascript"> // UTC 1970.1.1 到 285616年 // Date日期对象 /* 1.四种方式创建 var now = new Date(); console.log(now); var xmas = new Date('December 25,1995 13:30:00'); console.log(xmas); var xmas = new Date(1995,11,25); console.log(xmas); var xmas = new Date(1995,11,25,14,30,0); console.log(xmas); */ var now = new Date(); // 常用方法 console.log(now.getDate()); //获取月份的第几天 (1~31) console.log(now.getMonth()); //获取月份 (0~11) console.log(now.getFullYear()); //获取年份 console.log(now.getDay()); //获取一星期中的第几天(0 ~ 6) console.log(now.getHours()); //获取小时(0~23); console.log(now.getMinutes()); //获取分钟(0~59); console.log(now.getSeconds()); //获取秒(0~59); // 日期格式化方法 console.log(now.toDateString()); //星期几 月 日 年 console.log(now.toTimeString()); //时 分 秒 时区 // 常用 console.log(now.toLocaleDateString()); // 2020/11/24 console.log(now.toLocaleTimeString()); //下午2:24:30 console.log(now.toLocaleString()); // 2020/11/24 下午2:24:30 console.log(now.toUTCString()); //Tue, 24 Nov 2020 06:24:30 GMT </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>返回用数字时钟格式的时间</title> </head> <body> <script type="text/javascript"> // 6:27:35 P.M. // 6:30:01 P.M. // 6:04:01 A.M. // :0 4 // : 30 function nowNumTime(){ var now = new Date(); var hour = now.getHours(); //0 ~ 23. //19 var minute = now.getMinutes(); var second = now.getSeconds(); // 18 > 12 ? 18-12 : 8 var temp = '' + (hour > 12 ? hour - 12 : hour); if(hour === 0){ temp = '12'; } temp = temp +(minute < 10 ? ':0': ":")+ minute; temp = temp +(second < 10 ? ':0': ":")+ second; temp = temp + (hour >= 12 ? ' P.M.': " A.M."); return temp; } var nownum = nowNumTime(); console.log(nownum); </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>字符串和数值相互转换</title> </head> <body> <script type="text/javascript"> var str = '13131.9090013'; // 字符串转数值类型 console.log(parseInt(str)); console.log(parseFloat(str)); console.log(typeof parseFloat(str)); var a = Number(str); console.log(isNaN(a)); //NaN var num = 1313.179; // 强制类型转换 console.log(num.toString()); console.log(typeof num.toString()); console.log(String(num)); // 隐式转换 console.log('' + num); console.log(''.concat(num)); console.log(Number(num.toFixed(2))); </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>字符串和数值相互转换</title> </head> <body> <script> var str='12333.12000256' //转换整型(字符串转换数值类型) console.log(parseInt(str)); console.log(parseFloat(str)); console.log(Number(str)); a =Number(str); console.log(isNaN(a)); //数值转换为字符串 var num =123.22 console.log(num.toString()); console.log(String(num)) //隐士转换 console.log(''+num); //获取指定小数位的的字符串 console.log(num.toFixed(1)); </script> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Globle对象</title> </head> <body> <script type="text/javascript"> // URI var uri = 'http://www.apeland.cn/web index.html?name=zhangsan'; // encodeURIComponent()编码 使用最多的方法 console.log(encodeURI(uri));//只能解析空格 console.log(encodeURIComponent(uri)); //使用做多 // 解码 decodeURIComponent() // decodeURI(encodeuri); // decodeURIComponent(encodeuri); </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>window对象</title>
</head>
<body>
<script type="text/javascript">
var a = 3;
console.log(window.a);
function hello(){
alert(window.a);
}
window.hello();
</script>
</body>
</html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Math对象</title> </head> <body> <script type="text/javascript"> // Math // var a = 3; // 方法 min() max() var max = Math.max(3,34,56,21); var min = Math.min(3,34,56,21); var arr = [1,2,32,23,45,21]; var max = Math.max.apply(null,arr); var min = Math.min.apply(null,arr); // var max= Math.max(arr[0],arr[1],arr[2]); console.log(max); console.log(min); // ceil() floor() round() var num = 24.8; console.log(Math.ceil(num)); //天花板函数 向上取整 console.log(Math.floor(num)); //地板函数 向下取整 console.log(Math.round(num)); //标准的四舍五入 // 随机数 random() 0 <= random<1 console.log(Math.random()); // 1.获取min到max之间的整数 // 2.获取随机颜色 rgb(0~255,0~255,0~255); // 3.随机验证码 四位 数字+ 字母 (大写) </script> </body> </html>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>练习</title>
</head>
<body>
<script type="text/javascript">
// 1.获取min到max之间的整数 (1~100)
function random(max,min){
return Math.floor(Math.random() * (max-min) + min);
}
// 2.获取随机颜色 rgb(0~255,0~255,0~255);
function randomColor(){
// var result
var r = random(0,256),g = random(0,256),b = random(0,256);
// 模板字符串 ``
var result = `rgb(${r},${g},${b})`;
return result;
}
var rc = randomColor();
console.log(rc);
document.body.style.backgroundColor = rc;
// 3.随机验证码 四位 数字+ 字母 (大写) 65Yz
function creatCode(){
// 设置默认的空的字符串
var code = '';
// 设置长度
var codeLength = 4;
var randomCode = [0,1,2,3,4,5,6,7,8,9,'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R', 'S','T','U','V','W','X','Y','Z'];
for(var i = 0; i < codeLength; i++){
// 设置随机范围 0~36
var index = random(0,36);
code += randomCode[index];
}
return code;
}
var rndcode = creatCode();
console.log(rndcode);
document.write(`<h1>${rndcode}</h1`)
</script>
</body>
</html>
33 异常处理
try { //这段代码从上往下运行，其中任何一个语句抛出异常该代码块就结束运行 var name = '' } catch (e) { // 如果try代码块中抛出了异常，catch代码块中的代码就会被执行。 //e是一个局部变量，用来指向Error对象或者其他抛出的对象 } finally { //无论try中代码是否有异常抛出（甚至是try代码块中有return语句），finally代码块中始终会被执行。 }