如何把字符串表达式转为可运算的表达式？
有字符串 expr = "sum = (A-B)*C";
sum ，A，B，C 为HTML中 <input id="sum, A , B ,C" value=""/> 的ID
我想通过JS处理后得到
total = ($("#A").val() - $("#B").val() )*$("#C").val();
$("#sum").val(total);
[解决办法]
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript"> var regx = /[^\/)%(\*\+=-]+/g; var expr = "sum = (A-B) * C"; expr = expr.replace(regx,function($1){ $1 = $1.replace(/\s*/g,""); return $1!=""?"document.getElementById('" + $1 + "').value":""; }); window.onload = function(){ eval(expr); }</script></head><body> <input id="sum" type="text" value="" /> <input id="A" type="text" value="3" /> <input id="B" type="text" value="4" /> <input id="C" type="text" value="5" /></body></html>
[解决办法]
<input id="sum" type="text" value="" /><input id="A" type="text" value="3" /><input id="B" type="text" value="4" /><input id="C" type="text" value="5" /><script type="text/javascript">var expr = "sum = (A-B) * C";var sum = 0;var A = $("#A").val();var B = $("#B").val();var C = $("#C").val();window.eval('(' + expr + ')');$("#sum").val(sum);</script>