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2021.6.10.19.01

作者:互联网

今天学了for循环还有对昨天if语句的拓展

if语句判断是否是闰年

<script>
    //判断是否是普通闰年还是世纪闰年
    var nianFen = prompt('请输入年份')
    if (isNaN(nianFen*1)==true|| nianFen<0) {
        alert('您输入的年份有误')
    }else if (nianFen % 4 == 0 && nianFen % 100 !=0) {
        alert('是普通闰年')
    }else if ( nianFen % 400 == 0){
        alert('是世纪闰年')
    }else {
        alert('不是闰年')
    }
    //判断是否是闰年
    // var year= prompt('请输入年份')*1
    // if (isNaN(year) ==true) {
    //     alert('您输入的年份有误')
    // }else {
    //     if ((year% 4  ===0 && year% 100 !== 0) || (year% 4  ===0 && year% 100 === 0)) {
    //         alert('是闰年')
    //     }else {
    //         alert('不是闰年')
    //     }
    // }
</script>

typeof判断数据类型

<script>
        //typeof    测试变量类型
        var x = 10;
        console.log(typeof x);//number
        var y = 'hello'
        console.log(typeof y);//string
        var z = true
        console.log(typeof z)//boolean;
        var a = undefined;
        console.log(typeof a);//undefined
        var  b = null;
        console.log(typeof b);//object

        var obj = {
            username:'Jie',
            age:18
        }
        console.log(typeof obj);//object
        var arr = [1,2,3,4]
        console.log(typeof arr);//object

        // var res = prompt('请输入年龄');
        // console.log(typeof res );//string 
        var res2 = confirm('确定删除吗?')
        console.log(typeof res2);//boolean
    </script>

拼接字符串和反引号

<script>
    var product = {
        pName:'MI11',
        pPrice:1999
    }
    var price = product.pPrice;
    var pname = product.pName;
    //拼接字符串
    document.write(price + '元起')
    document.write('<p class="price">'+price+'元起</p>')

    document.write('<p class="pname">'+pname+'手机</p>')
    document.write( '<div><p class="pname">'+pname+'手机</p> <p class="price">'+price+'元起</p> </div>'
    )
    //反引号
    document.write(`
        <div>
        <p class="pname">${pname}手机</p> 
        <p class="price">${price}元起</p>
         </div>
    `)

    
</script>

数组

<script>
    // 数组: 用来表示一组数据的集合
    // 元素 索引(从0开始)
    
    var arr = ['a','b','c','d'];
    //1.根据索引访问数组中的元素
    console.log(arr[1]);
    //2.修改数组中元素
    arr[1] = 'b1';
    //console.log(arr);
    //3.添加元素
    arr[5] = 'e';
    console.log(arr);
    console.log(arr[4]);//undefined
    //4.length 属性 获取数组的长度(元素的个数)
    console.log(arr.length);//6
</script>

运算

<script>
    var x = 10;
    var y = '5';
    //var z = x+y;//105 此处是拼接字符串

    //var z = x - y ;//5 - 有隐式转换的作用
    // true=>1  false=>0
    //var x = x - y + true;//6
    var z = x * y - 'true' //NaN

    console.log(z);
</script>

for循环语句

<script>
    //循环
    // for (let how = 0; how < 100; how++) {
    //     console.log(hello world);//重复执行代码
    // }
    //for 循环的执行流程

    /*
        var i= 0
        if(i<100){执行花括号中的代码 }
        i++;
        if(i<100){执行花括号中的代码 }
        i++;
        ...
        if(i<100){执行花括号中的代码 }
        i++;    
        if(i<100) 不符合条件 终止循环
    */ 
//    for (let ou = 0; ou < 11; ou+=2) {
//        console.log(ou);
//    }
//    for (let ou = 0; ou < 11; ou++) {
//        if (ou%2 ==0) {
//            console.log(ou);
//        }
//    }
   var html = '<ul>';
   for (let i = 1; i < 11; i++){
        html += `<li>item${i}</li>`
   }
   html = html+'</ul>';
   document.write(html)
   //求0-100之间数的和
   var b = 0
   for (let a = 0; a <=10; a++) {
       b = b+a
   }
   console.log(b);
</script>

遍历数据

<script>
    // var nameArr = ['小米1','小米2','小米3','小米4','小米5','小米6','小米7']
    // for (let i = 0; i < nameArr.length; i++) {
    //     var pname = nameArr[i];
    //     document.write(`<p>${pname}</p>`)
    // }
    var proArr = [
        {
            pname:'小米1',
            price:1999,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/61454401f855cf5ed64747a6ac04bae5.jpg?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米2',
            price:2199,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/8909080ddb0851af0b87530e2927844f.jpg?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米11',
            price:3999,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/5dc32ec73299ff79556dcd1cf0f0ac11.png?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米10',
            price:2599,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/eb69512d9d6430d865d457ec52eebb51.png?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米8',
            price:2399,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/34caee2c867bfd8c5e0dc2d8c663e121.jpg?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米6',
            price:999,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/cb554f30eaa0316b0a736c3d59f21584.png?thumb=1&w=250&h=250&f=webp&q=90'
        },{
            pname:'小米7',
            price:1699,
            imgUrl:'https://cdn.cnbj1.fds.api.mi-img.com/mi-mall/3b7fbb6fe07907c60f08358adab5adfe.png?thumb=1&w=250&h=250&f=webp&q=90'
        },
    ];
    //要求:将以上数组上 产品的名称 显示到页面上
    document.write(`<ul>`)
    for (let i = 0; i < proArr.length; i++) {
        var a = proArr[i].pname;
        var b = proArr[i].imgUrl;
        var c = proArr[i].price;
        document.write(`
                    <li>
                        <img src="${b}">
                        <h6>${a}</h6>
                        <p>${c}元起</p>
                    </li>
        `)
    }
    document.write('</ul>')
</script>

遍历数组

<script>
    //遍历数组 利用for循环 获取数组中的每一组元素
    var arr = ['a','b','c','d','e','f'];
    for (let a = 0; a < arr.length; a++) {
        console.log(arr[a]);
    }
    var price = [100,200,300,400,500]
    for (let x = 0; x < price.length; x++) {
        console.log(price[x]*0.8);
    }
    //[100,200,300,400,500] => [80,160,240,320,400]
    for (let y = 0; y < price.length; y++) {
        price[y] = price[y]*0.8
    }
    console.log(price);
</script>

今天留下的作业很难 真的很难感觉

标签:01,console,log,2021.6,price,10.19,pname,var,250
来源: https://www.cnblogs.com/wangjie677/p/14872437.html