老师点击退位键显示undefind
来源：3-5 计算器细节完善
Buck_messic
2020-08-03 22:38:22
下面是代码：
<!DOCTYPE html>
<html>
<head>
<title></title>
<link rel="stylesheet" type="text/css" href="cals.css">
<script type="text/javascript" src="index.js"></script>
<script type="text/javascript"></script>
<body onload="init()">
<div id="div1">
<div id="div2">
<input type="text" name="num" id="num"/>
</div>
<div id="div3">
<input type="button" value="c" name="" id=""/>
<input type="button" value="←" name="" id=""/>
<input type="button" value="+/-" name="" id=""/>
<input type="button" value="/" name="" id=""/>
<input type="button" value="1" name="" id=""/>
<input type="button" value="2" name="" id=""/>
<input type="button" value="3" name="" id=""/>
<input type="button" value="*" name="" id=""/>
<input type="button" value="4" name="" id=""/>
<input type="button" value="5" name="" id=""/>
<input type="button" value="6" name="" id=""/>
<input type="button" value="-" name="" id=""/>
<input type="button" value="7" name="" id=""/>
<input type="button" value="8" name="" id=""/>
<input type="button" value="9" name="" id=""/>
<input type="button" value="+" name="" id=""/>
<input type="button" value="0" name="" id=""/>
<input type="button" value="." name="" id=""/>
<input type="button" value="=" name="" id=""/>
<input type="button" value="m" name="" id="imooc"/>
</div>
</div>
</body>
</html>
js代码：
function init(){
var num=document.getElementById("num");
num.value=0;
num.disabled="disabled";
var oButton=document.getElementsByTagName("input");
var btn_num1;
var fh;
for(var i=0;i<oButton.length;i++){
oButton[i].onclick=function(){
if(isNumber(this.value)){
if(isNull(num.value)){
num.value=this.value;
}else{
num.value=num.value+this.value;
}
}else{
var btn_num=this.value;
switch(btn_num){
case "+":
btn_num1=Number(num.value);
num.value=0;
fh="+";
break;
case "-":
btn_num1=Number(num.value);
num.value=0;
fh="-";
break;
case "*":
btn_num1=Number(num.value);
num.value=0;
fh="*";
break;
case "/":
btn_num1=Number(num.value);
num.value=0;
fh="/";
break;
case ".":
num.value=dec_number(num.value);
break;
case "←":
num.value=back(num.value);
break;
case "c":
num.value="0";
break;
case "+/-":
num.value=sing(num.value);
break;
case "=":
switch(fh){
case "+":
num.value=btn_num1+Number(num.value);
break;
case "-":
num.value=btn_num1-Number(num.value);
break;
case "*":
num.value=btn_num1*Numbert(num.value);
break;
case "/":
if(Number(num.value)==0){
alert("除数不能为0")
num.value=0
}else{
num.value=btn_num1/Number(num.value);}
break;
}
break;
}
}
}
}
}
/*验证文本框是否为空或者0*/
function isNull(n){
if(n=="0"||n.length==0){
return true;
}else{
return false;
}
}
function isNumber(n){
//if(!isNaN(n)){
// return true;//参数是数字
//}else{
// return false;//参数不是数字
//}
return !isNaN(n);
}
function back(n){
n=n.substr(0,n.length-1);
if(isNull(n)){
n="0";
}
return n;
}
function dec_number(n){
if(indexOf(".")==-1){
n=n+".";
}else{
return n
}
}
function sing(n){
n=Number(n)*-1
return n;
}
1回答
-
时间，
2020-08-04
同学，你好。运行同学的代码没有问题，同学可以看下js代码是否保存，或者在退位键位置输出下num.value的值，看是否可以得到正确结果。
如果我的回答解决了您的疑惑，请采纳！祝学习愉快~~~~
0
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