用JS 写一个加减乘除的小列子 要的效果是 下拉加减乘除自动运算
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来虐小学生
<select name="xiala" size="1" > <option value="+" selected="selected" id="yusuanfu">+</option> <option id="yusuanfu" value="-">-</option> <option id="yusuanfu" value="*">*</option> <option id="yusuanfu" value="/">/</option> </select>这一部分代码有问题，<select name="xiala" id="yunsuanfu" size="1" > <option value="+">+</option> <option value="-">-</option> <option value="*">*</option> <option value="/">/</option></select>我的全部代码，用你的经过删改的，是通过点击完成你的作用的<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title></title> <script type="text/javascript" > function yunsuan(){ var _num1=document.getElementById("_num1").value; _num1 =parseInt(_num1); var _num2=document.getElementById("_num2").value; _num2 =parseInt(_num2); var yunsuanfu=document.getElementById("yunsuanfu").value; var sum; switch(yunsuanfu){ case '+': sum=_num1+_num2; break; case '-' : sum=_num1-_num2; break; case '*' : sum=_num1*_num2; break; case '/' : sum=_num1/_num2; break; default: break; } document.getElementById("sum").innerHTML = sum; } </script></head><body><input type="text" value="5" id="_num1"/><select name="xiala" id="yunsuanfu" size="1" > <option value="+">+</option> <option value="-">-</option> <option value="*">*</option> <option value="/">/</option></select><input type="text" value="6" id="_num2"/><input type="button" value="=" onclick="yunsuan()"><span id="sum"> </span></body></html> -
qq_严瑞_0
<title></title> <script type="text/javascript" > window.onload=function(){ var _num1=document.getElementById("_num1").value; _num1 =parseInt(_num1); var _num2=document.getElementById("_num2").value; _num2 =parseInt(_num2); var yunsuanfu=document.getElementById("yunsuanfu").value; var sum; switch(yunsuanfu){ case '+': sum=_num1+_num2; break; case '-' : sum=_num1-_num2; break; case '*' : sum=_num1*_num2; break; case '/' : sum=_num1/_num2; break; default:没有此语句 ; break; } document.getElementById("sum").innerHTML=sum; </script> </head> <body> <input type="text" value="5" id="_num1"/> <select name="xiala" size="1" > <option value="+" selected="selected" id="yusuanfu">+</option> <option id="yusuanfu" value="-">-</option> <option id="yusuanfu" value="*">*</option> <option id="yusuanfu" value="/">/</option> </select> <input type="text" value="6" id="_num2"/> = <span id="sum"> </span> </body></html>大神帮看看 -
杰杰就是我
其实你可以获取到select的值 ,然后套用 switch 进行比较 ,比如你选择 '+'的操作switch(tag){ case '+': sum = num1+num2; break; case '-': ............. }可以这样来操作, 你判断选择符那里有问题 , 因为 你用的是 sum = num1+num2 , 所以执行的永远是第一条语句 不懂可以继续提问
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