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怎么優(yōu)化這串代碼

<!DOCTYPE?html>
<html>
?<head>
??<title>?事件</title>??
??<script?type="text/javascript">
???function?count(){
???????var?a?=?parseInt(document.getElementById("txt1").value);
???????var?b?=?parseInt(document.getElementById("txt2").value);
???????switch(document.getElementById("select").value){
???????????case?("+"):?document.write(a+b);break;
???????????case?("-"):?document.write(a-b);break;
???????????case?("*"):?document.write(a*b);break;
???????????case?("/"):?document.write(a/b);break;
???????}
???}
??</script>?
?</head>?
?<body>
???<input?type='text'?id='txt1'?/>?
???<select?id='select'>
		<option?value='+'>+</option>
		<option?value="-">-</option>
		<option?value="*">*</option>
		<option?value="/">/</option>
???</select>
???<input?type='text'?id='txt2'?/>?
???<input?type='button'?value='?=?'/>?
???<input?type='text'?id='fruit'?onfocus="count()"/>???
?</body>
</html>

怎么能夠使得點(diǎn)擊等于后，結(jié)果顯示在第三個(gè)文本框

Luffykaiyuan4240471

2017-05-08

源自：JavaScript進(jìn)階篇 6-11

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1 回答

ziom 回答被采納 +3 積分
2017-05-09

switch那一段改成如下試試：

var?fruit?=?document.getElementById(?"fruit");
switch(document.getElementById("select").value){???????????
????case?("+"):?fruit.value=(a+b);break;
????case?("-"):?fruit.value=(a-b);break;
????case?("*"):?fruit.value=(a*b);break;
????case?("/"):?fruit.value=(a/b);break;
}