练习
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zuoye/js/a.html
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zuoye/js/a.html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Document</title>
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</head>
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<body>
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<script>
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var time=1
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var newtime=time++
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console.log(time,newtime)
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</script>
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</body>
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</html>
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# 运算符
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* 完成教案后面的4个练习
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* 预习if语句，函数定义传参 ，定义一个函数 返回值实现两个参数的加减乘除 取余 乘方和相加的计算器功能
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* 完成逻辑运算符后面的9个练习
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zuoye/js/pdfs/基础.pdf
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zuoye/js/pdfs/基础.pdf
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zuoye/js/pdfs/运算符.pdf
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zuoye/js/pdfs/运算符.pdf
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zuoye/js/基础.md
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zuoye/js/基础.md
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# js 基础练习
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* 写出四种js引入方式并举例
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* 下面两段代码，说明js文件的加载顺序并解释原因
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demo1:
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```
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<script async src="js/vendor/jquery.js"></script>
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<script async src="js/script2.js"></script>
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<script async src="js/script3.js"></script>
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```
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demo2
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```
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<script defer src="js/vendor/jquery.js"></script>
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<script defer src="js/script2.js"></script>
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<script defer src="js/script3.js"></script>
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```
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* 如果浏览器不支持javascript的语法需要在页面上提示您的浏览器不支持javascript 运行 如何实现
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* 列举几种js 交互方式
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* js的组成
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* JavaScript 如何与 HTML 和 CSS 协同工作
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* 在外部文件中放置js脚本有什么优势
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变量和常量
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* 如何交换两个变量的值
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* 字面量和变量的关系及区别
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* 变量命名规则
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* 下面代码执行结果为 原因是
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```
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var obj1 = new Object();
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var obj2 = obj1;
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obj1.name = "Nicholas";
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alert(obj2.name);
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```
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* 用一行语句声明5个变量 其中值包有一个只声明不赋值 其他分别为null 数值 字符串 布尔
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数据类型
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* 数据类型可以分为哪几类 有什么区别
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* 如何实现功能 当浏览器不支持javascript脚本的时候 给用户在页面上提示“您的浏览器不支持javascript 脚本，请尽快升级浏览器”
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* typeof 检测数据类型的返回值都有什么 分别代表什么意思
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* 类型转换相关
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1. 输入两个数字，点求和弹出两个数字相加的结果。
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1. 输入框的默认value进行相加，结果是进行了字符串相加，而非数字相加。
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2. 将value的值进行parseInt，之后再相加，就是数字相加的结果了。
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如果输入12+abc，会是什么结果？ 你得到了什么结论
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3.isNaN，检测输入框的内容是不是NaN。true为真，false为假。
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4.写出下面的执行结果
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1 + '1'
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true + 0
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{}+[]
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4 + {}
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4 + [1]
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'a' + + 'b'
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console.log ( [] == 0 )
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console.log ( ! [] == 0 )
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console.log ( [] == ! [] )
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console.log ( [] == [] )
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console.log({} == !{})
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console.log({} == {})
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1. 定义一个变量存储数据1234，分别输出个位，十位，百位，千位数字
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2. 输入两个数字，相减四舍五入（.toFixed() 把保留几位小数写在括号里）
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3. 从弹框中输入一个字符，判断这个字符是否是英文字母，数字，汉字（4e00-9fa5）
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4. 下面代码的输出结果
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console.log(10 + " cats");
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console.log(10 * " cats");
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Boolean([])
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console.log(10 + "2");
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console.log(10 - "2");
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Number("3")
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console.log(10 / "2");
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console.log(10 * "2");
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String(false)
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console.log(10 * " 2");
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console.log("10" * "2");
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console.log(Object(undefined));
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console.log(Object(null));
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5. 下面代码的执行结果
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var str = "abc";
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str[0] = "d";
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console.log(str[1]="e");
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console.log(str[0]);
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console.log(str);
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var num = [1,2,3];
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num[0] = "a";
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console.log(num);
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1. 下面代码的执行结果
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var obj1 = {age: 22};
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var obj2 = obj1;
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console.log(obj1 === obj2);
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obj2.age = 18;
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console.log(obj1 === obj2);
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2. 解释10，11结果出现的原因 并归纳基本数据类型和引用数据类型的区别
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3. 下面代码的输出结果
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var obj1 = {age: 22};
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var obj2 = obj1;
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console.log(obj1 === obj2);
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obj2.age = 18;
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console.log(obj1 === obj2);
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console.log("1" instanceof String);
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console.log(("1").constructor === String);
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console.log((1).constructor === Number);
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console.log((true).constructor === Boolean);
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console.log(([]).constructor === Array);
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console.log((function() {}).constructor === Function);
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console.log(({}).constructor === Object);
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console.log(1 instanceof Number);
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console.log(true instanceof Boolean);
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console.log([] instanceof Array);
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console.log(function(){} instanceof Function);
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console.log({} instanceof Object);
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var test = Object.prototype.toString;
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console.log(test.call("str"));
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console.log(test.call(1));
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console.log(test.call(true));
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console.log(test.call(null));
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console.log(test.call(undefined));
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console.log(test.call([]));
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console.log(test.call(function() {}));
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console.log(test.call({}));
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# 语句
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* 完成jsinfo相关练习
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* 实现 fizzBuzz 函数，参数 num 与返回值的关系如下：
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1、如果 num 能同时被 3 和 5 整除，返回字符串 fizzbuzz
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2、如果 num 能被 3 整除，返回字符串 fizz
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3、如果 num 能被 5 整除，返回字符串 buzz
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4、如果参数为空或者不是 Number 类型，返回 false
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5、其余情况，返回参数 num
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示例
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输入：15
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输出：fizzbuzz
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# 数组
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* 计算给定数组 arr 中所有元素的总和
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输入 [ 1, 2, 3, 4 ]
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Before Width: | Height: | Size: 32 KiB After Width: | Height: | Size: 32 KiB |
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zuoye/js/语句.md
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zuoye/js/语句.md
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# 语句
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* 完成jsinfo相关练习
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* 判断闰年
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* 根据分数划分等级（四个等级）
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* 用switch完成查询水果的价格（五种水果 如果不在列表里就提示未上架）
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* 在弹框中输入你的工资，大于等于20000显示高工资，8000-20000显示中高工资，小于8000显示普通工资
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* 实现 fizzBuzz 函数，参数 num 与返回值的关系如下：
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1、如果 num 能同时被 3 和 5 整除，返回字符串 fizzbuzz
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2、如果 num 能被 3 整除，返回字符串 fizz
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3、如果 num 能被 5 整除，返回字符串 buzz
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4、如果参数为空或者不是 Number 类型，返回 false
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5、其余情况，返回参数 num
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示例
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输入：15
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输出：fizzbuzz
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Before Width: | Height: | Size: 30 KiB After Width: | Height: | Size: 30 KiB |
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zuoye/js/运算符.md
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zuoye/js/运算符.md
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# 运算符相关
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1. 两个自定义变量进行相等对比，弹出运算结果。 （分别放两个按钮 第一个弹出==的比较结果 第二个弹出 ===的比较结果）
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2. 完成计算器的功能 输入两个数 输出计算结果 具体计算功能包含 加减乘除成方取余 每个计算方式分别放按钮 点击输出计算结果
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3. 用js 取模实现表格的隔行换色
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4. 求商取模应用于秒转时间 输入框单位为秒
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思路：不管输入框获取到的数字是多少，都执行除60取分钟，除600取小时，最后取模为秒数。通过parseInt取整数
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5. 判断是否为两位数
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6. 写出运算符优先级
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7. 计算年龄案例：输入生日输出年龄 并且判断是否能进入网吧
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8. 运算符的优先级
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9. 下面代码的执行结果为
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```
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var age = 29;
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var anotherAge = --age + 2;
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alert(age);
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alert(anotherAge);
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var time=1
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var newtime=time++
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console.log(time,newtime)
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```
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11. 下面代码的执行结果为
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```
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<script>
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var a =1;
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function test(){
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alert(a);
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var a = 2;
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alert(a);
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}
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test();
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alert(a);
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</script>
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```
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12. 下面代码的执行结果为
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```
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var x = 7;
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x += 8;
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console.log(x)
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var y=7
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y=+8;
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console.log(y)
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```
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13. 下面代码的执行结果为：
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```
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txt1 = "Hello ";
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txt1 += "Kitty!";
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console.log(txt1)
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console.log(x = 7 + 8;)
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console.log(y = "7" + 8;)
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console.log(z = "Hello" + 7;)
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```
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14. 已知 x=5 分别写出下列语句的打印结果
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x == 8
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x == 5
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x == "5"
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x === 5
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x === "5"
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x != 8
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x !== 5
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x !== "5"
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x !== 8
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x > 8
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x < 8
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x >= 8
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x <= 8
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15. 已知 x=6 y=3 分别写出下列语句的打印结果
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x < 10 && y > 1
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x == 5 || y == 5
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!(x == y)
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16. 已知现有fish="23"
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var cat = (fish < 18) ? "再来一筐锦鲤":"吃饱啦";
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最后的cat 打印结果为
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17. 写出下面的打印结果
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2 < 12
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2 < "12"
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2 < "John"
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2 > "John"
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2 == "John"
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"2" < "12"
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"2" > "12"
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"2" == "12"
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18. 写出下面的打印结果
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```
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txt1="What a very ";
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txt2="nice day";
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txt3=txt1+txt2;
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console.log(txt3)
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var x = 1;
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x = -x;
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alert( x );
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var x = 1, y = 3;
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alert( y - x );
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```
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19. 写出下面的打印结果
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```
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alert( 5 % 2 );
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alert( 8 % 3 );
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alert( 2 ** 2 );
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alert( 2 ** 3 );
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alert( 2 ** 4 );
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alert( 4 ** (1/2) );
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alert( 8 ** (1/3) );
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alert( '1' + 2 );
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alert( 2 + '1' );
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alert(2 + 2 + '1' );
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var x = 1;
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alert( +x );
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var y = -2;
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alert( +y );
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// 转化非数字
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alert( +true );
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alert( +"" );
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var apples = "2";
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var oranges = "3";
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alert( apples + oranges );
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alert( Number(apples) + Number(oranges) );
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```
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20. 运算符优先级
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21. 下面代码的执行结果为
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```
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let a = 1;
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let b = 2;
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let c = 3 - (a = b + 1);
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alert( a );
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alert( c );
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```
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```
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let a, b, c;
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a = b = c = 2 + 2;
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alert( a );
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alert( b );
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alert( c );
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let n = 2;
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n += 5;
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n *= 2;
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alert( n );
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let n = 2;
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n *= 3 + 5;
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alert( n );
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```
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22. 下面代码的打印结果为
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```
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alert( true || true ); // true
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alert( false || true ); // true
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alert( true || false ); // true
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alert( false || false ); // false
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```
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```
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alert( 1 || 0 );
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alert( null || 1 );
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alert( null || 0 || 1 );
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alert( undefined || null || 0 )
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var firstName = "";
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var lastName = "";
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var nickName = "SuperCoder";
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alert( firstName || lastName || nickName || "Anonymous");
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```
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23. 下面代码会执行嘛 为什么
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```
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true || alert("not printed");
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false || alert("printed");
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```
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24. 下面代码的执行结果
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```
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alert( 1 && 0 );
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alert( 1 && 5 );
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alert( null && 5 );
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alert( 0 && "no matter what" )
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alert( 1 && 2 && null && 3 )
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alert( 1 && 2 && 3 )
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alert( !!"non-empty string" );
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alert( !!null );
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alert( Boolean("non-empty string") );
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alert( Boolean(null) );
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alert( null || 2 || undefined );
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alert( alert(1) || 2 || alert(3) )
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alert( alert(1) && alert(2) );
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alert( null || 2 && 3 || 4 );
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```
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附加
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游戏开始时，显示12个图像的背面，用鼠标点击其中任意一张，即可显示图像的正面，如果点击了两张，则显示出两张图像的正面。如果点击过的两张图像是相同的图像，则将图像从界面中移除
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