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计算器模拟
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="content-type" content="text/html" charset="utf-8"/>
<style>
.comp{
width: 500px;
min-height: 200px;
box-shadow: 3px 3px 3px gray;
margin: 0 auto;
border: 1px solid #efefef;
padding: 20px 100px;
background: gray;
border-radius: 5px;
}
#input1{
margin: 10px 0 ;
}
</style>
<title>计算器模拟</title>
</head>
<body>
<div class="comp">
<form>
<input type="text" name="input1" id="input1" />
<select id="tag">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type="text" name="input2" id="input2" />
<button type="button" >计算</button>
</form>
<p >结果:</p>
<p id="result"></p>
</div>
<script>
//获取按钮
let btn = document.getElementsByTagName("button")[0];
let input1 = document.getElementById('input1');
let input2 = document.getElementById('input2');
let tags = document.getElementById('tag');
let p = document.getElementById('result');
btn.onclick = function (){
let num1 = 0;
let num2 = 0;
let tag = tags.value;
result = 0;
//非空判断/数据字符串解析处理
if(input1.value.length===0){
alert('第一个数不能为空');
input1.focus();
return false;
}else if(isNaN(input1.value)){
alert('第一个数字符');
input1.focus();
return false;
}else if(input2.value.length===0){
alert('第一个数不能为空');
input1.focus();
return false;
}else if(isNaN(input2.value)){
alert('第一个数字符');
input1.focus();
return false;
}else{
num1 = parseFloat(input1.value);
num2 = parseFloat(input2.value);
}
//数据运算
if(tag==='+'){
result = num1+num2;
}else if(tag==='-'){
result = num1-num2;
}else if(tag==='*'){
result = num1*num2;
}else{
if(num2===0)
{
alert('除数不能为0');
num2='';
return false;
}
result = num1/num2;
}
p.innerHTML= result;
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例