< 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 >Documenttitle >
< script type = "text/javascript" >
function cal(){
var nums = document.getElementsByName("num");
var sz = document.getElementsByName("js");
var result = document.getElementsByName("rs");
var n1 = parseFloat(nums[0].value);
var n2 = parseFloat(nums[1].value);
/*parseFloat() 函数可解析一个字符串,并返回一个浮点数。
该函数指定字符串中的首个字符是否是数字。如果是,则对字符
串进行解析,直到到达数字的末端为止,然后以数字返回该数字,
而不是作为字符串。
*/
switch(sz[0].value){
case "add" :
result[0].value = n1 + n2 ;
break;
case "min" :
result[0].value = n1 - n2 ;
break;
case "mul" :
result[0].value = n1 * n2 ;
break;
case "div" :
result[0].value = n1/n2;
break;
}
}
script >
head >
< body >
< div align = "center" >
< input type = "text" name = "num" value = "" onkeyup = "value=value.replace(/^\D*(\d*(?:\.\d{0,2})?).*$/g, '$1')" />
< select name = "js" size = "1" >
< option value = "add" >+option >
< option value = "min" >-option >
< option value = "mul" >*option >
< option value = "div" >/option >
select >
< input type = "text" name = "num" value = "" onkeyup = "value=value.replace(/^\D*(\d*(?:\.\d{0,2})?).*$/g, '$1')" />
=
< input type = "text" name = "rs" value = "" />< br >
< button id = "btn" onclick = "cal()" >计算button >
div >
body >
html >
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