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How to implement calculator function using javascript

王林Original: 2021-11-03 17:13:203645browse

How to use javascript to implement the calculator function: [function init(){ var num=document.getElementById("num"); num.value=0; var btn_num1; var fh; ...].

#The operating environment of this article: windows10 system, javascript 1.8.5, thinkpad t480 computer.

Presumably everyone has written calculator functions in the process of learning programming languages, such as using php, java, python and other languages. So have you ever used javascript to implement the calculator function? In fact, the principles are the same, let’s take a look together!

HTML code:

<!DOCTYPE html>
<html>
<head>
	<title>js计算器</title>
<link rel="stylesheet" type="text/css"href="index.css">
<script type="text/javascript" src="index.js">
</script>
</head>
<body onload="init()">
	<!-- 1个文本框10个数字....20个按钮 -->
<div id="div1">
	<form action="">
	<div id="div2">
		<input type="text" name="num" disabled="disabled" id="num" value="0">
	</div>
	</form>
	<div id="div3">
		<input type="button" name="" value="C" id="baidu">
		<input type="button" name="" value="←" id="">
		<input type="button" name="" value="+/-" id="">
		<input type="button" name="" value="/" id="">
		<input type="button" name="" value="7" id="">
		<input type="button" name="" value="8" id="">
		<input type="button" name="" value="9" id="">
		<input type="button" name="" value="*" id="">
		<input type="button" name="" value="4" id="">
		<input type="button" name="" value="5" id="">
		<input type="button" name="" value="6" id="">
		<input type="button" name="" value="-" id="">
		<input type="button" name="" value="1" id="" >
		<input type="button" name="" value="2" id="" >
		<input type="button" name="" value="3" id="" >
		<input type="button" name="" value="+" id="">
		<input type="button" name="" value="0" id="">
		<input type="button" name="" value="=" id="">
		<input type="button" name="" value="." id="">
		<input type="button" name="" value="AC" id="">
	</div>
</div>
</body>
</html>`

JS code:

function init(){
	var num=document.getElementById("num");
	num.value=0;
	var btn_num1;
	var fh;
	num.disabled="disabled";
	// var n1=document.getElementById("n1");
	// n1.οnclick=function(){
	// }
	var oButton=document.getElementsByTagName("input");
	for(var i=0;i<oButton.length;i++){
		oButton[i].onclick=function(){
			if(isnumber(this.value)){
				//num.value=(num.value+this.value)*1;//把默认0消除
			if(isNull(num.value)){
				num.value=this.value;
			}else{
				num.value=num.value+this.value;
			}
			}else{
			//测试功能是否正确
				// alert("bushishuzi")
				var btn_num=this.value;
				//测试功能是否正确（弹窗）
				// alert(btn_num);
				switch(btn_num){
					case "+":
					// alert(11);
					btn_num1=num.value*1;//=parseInt(num.value)这个也可以,后面的话需要改为number
					num.value=0;
					fh="+";
					break;
					case "-":
					btn_num1=num.value*1;
					num.value=0;
					fh="-";
					break;
					case "*":
					btn_num1=num.value*1;
					num.value=0;
					fh="*";
					break;
					case "/":
					btn_num1=num.value*1;
					num.value=0;
					fh="/";
					break;
					case ".":
					num.value=dec_number(num.value);
					break;
					case "←":
					num.value=back(num.value);
					break;
					case "+/-":
					num.value=sign(num.value);
					break;
					case "AC":
					num.value="0";
					break;
					case "C":
					init_baidu();
					break;
					case "=":
					switch(fh){
						case"+":
						num.value=btn_num1+num.value*1;
						break;
						case"-":
						num.value=btn_num1-num.value*1;
						break;
						case"*":
						num.value=btn_num1*num.value*1;
						break;
						case"/":
						if(num.value==0){
							num.value=0;
							alert("除数不能为0");
						}else{
							num.value=btn_num1/num.value*1;
						}
						break;
					}
					break;
				}
			}
		}
	}
}
//小数点的功能
function dec_number(n){
	if(n.indexOf(".")==-1){
		n=n+".";
	}
	return n;
}
//验证文本框是否为空或者为0
function isNull(n){
	if(n*1==0||n.length==0){
		return true;
	}else{
		return false;
	}
}
//退位键
function back(n){
	n=n.substr(0,n.length-1);
	if(isNull(n)){
		n="0";
	}
	return n;
}
//正负号+/-
function sign(n){
	if(n.indexOf("-")==-1){
		n="-"+n;
	}else{
		n=n.substr(1,n.length);
	}
	return n;
}
//isNaN:不能转换成数字：true,可以转换成数字是false
function isnumber(n){
	return !isNaN(n);
	}
	//C按钮使用一个超级链接，链接到百度，这个可以随便发挥
function init_baidu(){
			window.location.href="http://www.baidu.com";
}

CSS code:

*{
	margin:0px;
	padding:0px;
}
div{
	width:170px;
}
#div1{
	top:60px;
	left: 100px;
	position:absolute;
}
input[type="button"]{
	width:30px;
	margin-right: 5px;
}
input[type="text"]{
	width:147px;
	text-align: right;
	background-color:white;
	border:1px solid;
	padding-right:1px;
	box-sizing:content-box;
}
input[type="button"]:hover{/*//伪类和按钮的使用*/
	background-color:white;
	border:1px solid;
}

Recommended learning: javascript video tutorial

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