看菜鸟教程学js
看菜鸟教程学js
数组
var cars=new Array();
cars[0]=“Saab”;
cars[1]=“Volvo”;
cars[2]=“BMW”;
var cars=new Array(“Saab”,“Volvo”,“BMW”);
数组下标是基于零的，所以第一个项目是 [0]，第二个是 [1]，以此类推。
JavaScript 对象
对象属性有两种寻址方式：
name=person.lastname;
name=person[“lastname”];
JavaScript 变量均为对象。当您声明一个变量时，就创建了一个新的对象。
除了基本的数据类型剩下的就是对象了。
<script>function Demo() {var obj = new Object();obj.name = "张思";obj.age = 12;obj.firstF = function () {};obj.secondF = function () {};return obj;}var one = Demo();// 调用输出document.write(one.age);</script>
var a = {name:"percy"};
var b;
b = a;
a.name = "zyj";
console.log(b.name); // zyj
b.age = 22;
console.log(a.age); // 22
var c = {name: "zyj",age: 22
};
看代码就可以看到。
不加括号就是问这个里面装的是什么，加了括号以后就是调用这个方法。
通过new Object来创建对象。
return相当于人家给你准备了这个东西，但是你需要去拿才可以拿到。
<!DOCTYPE html>
<html><head><meta charset="utf-8" /><title>菜鸟教程(runoob.com)</title></head><body><button onclick="demo()">点我</button><script>function demo() {alert("大叫三声我是傻逼");}</script></body>
</html>
<!DOCTYPE html>
<html><head><meta charset="utf-8" /><title>菜鸟教程(runoob.com)</title></head><body><button id="1" onclick="demo()">点我</button><script>function demo(a, b) {return a * b;}document.getElementById("1").innerHTML = demo(3, 4);</script></body>
</html>
https://www.runoob.com/js/js-functions.html
前端中id、name、value的区别
https://blog.csdn.net/wem603947175/article/details/83004364?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522163037944916780265444957%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=163037944916780265444957&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2allsobaiduend~default-1-83004364.first_rank_v2_pc_rank_v29&utm_term=id%2Cname%2Cvalue&spm=1018.2226.3001.4187
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8" /><meta http-equiv="X-UA-Compatible" content="IE=edge" /><meta name="viewport" content="width=device-width, initial-scale=1.0" /><title>做一个计算器</title><style>td {width: 100px;}</style><script>function add() {var firstnumber = Number(document.getElementById("first").value);var secondnumber = Number(document.getElementById("twice").value);// console.log(typeof firstnumber);console.log(firstnumber);console.log(secondnumber);console.log(firstnumber + secondnumber);document.getElementById("result").innerHTML =firstnumber + secondnumber;}</script></head><body><table border="1" style="position: center"><tr><td>第一个数</td><td><input type="text" id="first" /></td></tr><tr><td>第二个数</td><td><input type="text" id="twice" /></td></tr><tr><td></td><td><button onclick="add()">+</button> <button onclick="jian()">-</button> <button onclick="cheng()">*</button> <buttononclick="chu()">/</button> </td></tr><tr><td>结果</td><td id="result"></td></tr></table></body>
</html>
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8" /><meta http-equiv="X-UA-Compatible" content="IE=edge" /><meta name="viewport" content="width=device-width, initial-scale=1.0" /><title>Document</title><script>var checkAll = false;console.log(checkAll); //falsefunction allcheck() {checkAll = !checkAll; //true 变为true以后checkAll本身就为true了console.log(checkAll);let inputs = document.getElementsByName("checkbox");for (var i = 0; i < inputs.length; i++) {inputs[i].checked = checkAll;}}</script></head><body>看书：<input type="checkbox" name="checkbox" value="1" /><br />写字：<input type="checkbox" name="checkbox" value="2" /><br />打飞机：<input type="checkbox" name="checkbox" value="3" /><br />玩游戏：<input type="checkbox" name="checkbox" value="4" /><br /><button onclick="allcheck()">全选/取消</button></body>
</html>