為什么無法輸出結(jié)果？
<!DOCTYPE?html>
<html?lang="en">
<head>
????<meta?charset="UTF-8">
????<meta?name="viewport"?content="width=device-width,?initial-scale=1.0">
????<meta?http-equiv="X-UA-Compatible"?content="ie=edge">
????<title>Document</title>
????<script?type="text/javascript">
????function?count(){
????????var?a=document.getElementById("text1").value?;
????????var?b=document.getElementById("text2".value)?;
????????var?c=document.getElementById("select").value?;
????????var?sum?=?""?;
????switch(c){
????????case?"+":
????????????sum?=?parseInt(a)?+?parseInt(b);
????????????break;
????????case?"-":
????????????sum=?parseInt(a)?-?parseInt(b);
????????????break;
????????case?"*":
????????????sum=?parseInt(a)?*?parseInt(b);
????????????break;
????????default:
????????????sum=?parseInt(a)?/?parseInt(b);
????}
????document.getElementById("sum1")=sum;
????}
????</script>
</head>
<body>
????<input?type="text"?id="text1"/>
????<select?id="select">
????????<option?value=?"+"?>+</option>
????????<option?value=?"-"?>-</option>
????????<option?value=?"*"?>*</option>
????????<option?value=?"/"?>/</option>
????</select>
????<input?type="text"?id="text2"/>
????<input?type="button"?value="計(jì)算"?onclick="count()"/>
????<input?type="text"?id="sum1"/>
</body>
</html>
2020-02-05
document.getElementById("sum1")=sum;這句少了.value