用JS实现简易计算器
首先创建结构和样式
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Documenttitle>
<style>
body{
margin:0;
padding:0;
background-color: #abcdef;
}
.cal{
width:560px;
height:100px;
margin:0 auto;
padding-top:300px;
}
style>
head>
<body>
<div class="cal">
<p>
<input type="text" class="num1" value="1">
<span class="sign">+span>
<input type="text" class="num2" value="1">
<span>=span>
<span class="res">2span>
p>
<p>
<input type="button" value="+">
<input type="button" value="-">
<input type="button" value="*">
<input type="button" value="/">
p>
div>
<script>
script>
body>
html>
添加javascript功能
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Documenttitle>
<style>
body{
margin:0;
padding:0;
background-color: #abcdef;
}
.cal{
width:560px;
height:100px;
margin:0 auto;
padding-top:300px;
}
style>
head>
<body>
<div class="cal">
<p>
<input type="text" class="num1" value="1">
<span class="sign">+span>
<input type="text" class="num2" value="1">
<span>=span>
<span class="res">2span>
p>
<p>
<input type="button" value="+" class="btn">
<input type="button" value="-" class="btn">
<input type="button" value="*" class="btn">
<input type="button" value="/" class="btn">
p>
div>
<script>
var cal=document.querySelector(".cal");
var num1=cal.querySelector(".num1");
var num2=cal.querySelector(".num2");
var sign=cal.querySelector(".sign");
var res=cal.querySelector(".res");
var btns=cal.querySelectorAll(".btn");
btns[0].onclick=add;
btns[1].onclick=subtract;
btns[2].onclick=multiply;
btns[3].onclick=divide;
function add(){
sign.innerHTML="+";
//由于DOM获取到的值都是字符串形式，因此进行操作时需要先转为number类型
res.innerHTML=Number(num1.value)+Number(num2.value);
}
function subtract(){
sign.innerHTML="-";
res.innerHTML=Number(num1.value)-Number(num2.value);
}
function multiply(){
sign.innerHTML="*";
res.innerHTML=Number(num1.value)*Number(num2.value);
}
function divide(){
sign.innerHTML="/";
res.innerHTML=Number(num1.value)/Number(num2.value);
}
script>
body>
html>
代码的优化：
循环实现绑定
给一个外部接口，用于新增运算
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Documenttitle>
<style>
body{
margin:0;
padding:0;
background-color: #abcdef;
}
.cal{
width:560px;
height:100px;
margin:0 auto;
padding-top:300px;
}
style>
head>
<body>
<div class="cal">
<p>
<input type="text" class="num1" value="1">
<span class="sign">+span>
<input type="text" class="num2" value="1">
<span>=span>
<span class="res">2span>
p>
<p>
<input type="button" value="+" class="btn" title="add">
<input type="button" value="-" class="btn" title="subtract">
<input type="button" value="*" class="btn" title="multiply">
<input type="button" value="/" class="btn" title="divide">
<input type="button" value="%" class="btn" title="mod">
p>
div>
<script>
var cal=document.querySelector(".cal");
var num1=cal.querySelector(".num1");
var num2=cal.querySelector(".num2");
var sign=cal.querySelector(".sign");
var res=cal.querySelector(".res");
var btns=cal.querySelectorAll(".btn");
//给每个按钮绑定事件
for(var i=0;i<btns.length;i++){
operate(i);
}
//运算函数
function operate(i){
var op=btns[i].value;//获取运算
var opName=btns[i].title;//获取运算名
//绑定事件
btns[i].onclick=function(){
sign.innerHTML=op;
res.innerHTML=operation[opName](Number(num1.value),Number(num2.value));
}
}
var operation={
add:function(n1,n2){
return n1+n2;
},
subtract:function(n1,n2){
return n1-n2;
},
multiply:function(n1,n2){
return n1*n2;
},
divide:function(n1,n2){
return n1/n2;
},
//给一个新增运算的接口
addOperation:function(name,fn){
//如果该运算不存在
if(!this.name){
this[name]=fn;
}
}
}
//新增取余运算
operation.addOperation("mod",function(n1,n2){
return n1%n2;
});
script>
body>
html>
