2021.6.10.19.01
阿新 • • 發佈：2021-06-10
今天學了for迴圈還有對昨天if語句的拓展
if語句判斷是否是閏年
<script>
//判斷是否是普通閏年還是世紀閏年
var nianFen = prompt('請輸入年份')
if (isNaN(nianFen*1)==true|| nianFen<0) {
alert('您輸入的年份有誤')
}else if (nianFen % 4 == 0 && nianFen % 100 !=0) {
alert('是普通閏年')
}else if ( nianFen % 400 == 0){
alert(
typeof判斷資料型別
<script>
//typeof 測試變數型別
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(
拼接字串和反引號
<script>
var product = {
pName:'MI11',
pPrice:1999
}
var price = product.pPrice;
var pname = product.pName;
//拼接字串
document.write(price + '元起')
document.write('<p class="price">'+price+'元起</p>')
document.write('<p class="pname">'+pname+'手機</p>')
document.write( '<div><p class="pname">'+pname+'手機</p> <p class="price">'+price+'元起</p> </div>'
)
//反引號
document.write(`
<div>
<p class="pname">${pname}手機</p>
<p class="price">${price}元起</p>
</div>
`)
</script>
陣列
<script>
// 陣列： 用來表示一組資料的集合
// 元素 索引（從0開始）
var arr = ['a','b','c','d'];
//1.根據索引訪問陣列中的元素
console.log(arr[1]);
//2.修改陣列中元素
arr[1] = 'b1';
//console.log(arr);
//3.新增元素
arr[5] = 'e';
console.log(arr);
console.log(arr[4]);//undefined
//4.length 屬性 獲取陣列的長度(元素的個數)
console.log(arr.length);//6
</script>
運算
<script>
var x = 10;
var y = '5';
//var z = x+y;//105 此處是拼接字串
//var z = x - y ;//5 - 有隱式轉換的作用
// true=>1 false=>0
//var x = x - y + true;//6
var z = x * y - 'true' //NaN
console.log(z);
</script>
for迴圈語句
<script>
//迴圈
// for (let how = 0; how < 100; how++) {
// console.log(hello world);//重複執行程式碼
// }
//for 迴圈的執行流程
/*
var i= 0
if(i<100){執行花括號中的程式碼 }
i++;
if(i<100){執行花括號中的程式碼 }
i++;
...
if(i<100){執行花括號中的程式碼 }
i++;
if(i<100) 不符合條件 終止迴圈
*/
// 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${i}</li>`
}
html = html+'</ul>';
document.write(html)
//求0-100之間數的和
var b = 0
for (let a = 0; a <=10; a++) {
b = b+a
}
console.log(b);
</script>
遍歷資料
<script>
// var nameArr = ['小米1','小米2','小米3','小米4','小米5','小米6','小米7']
// for (let i = 0; i < nameArr.length; i++) {
// var pname = nameArr[i];
// document.write(`<p>${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：將以上陣列上 產品的名稱 顯示到頁面上
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>
遍歷陣列
<script>
//遍歷陣列 利用for迴圈 獲取陣列中的每一組元素
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>
今天留下的作業很難 真的很難感覺