javascript(js)使用eval方法加密过的函数解密方法

<script> a=62; function encode() { var code = document.getElementById('code').value; code = code.replace(/[ ]+/g, ''); code = code.replace(/'/g, "/'"); var tmp = code.match(/(w+)/g); tmp.sort(); var dict = []; var i, t = ''; for(var i=0; i<tmp.length; i++) { if(tmp[i] != t) dict.push(t = tmp[i]); } var len = dict.length; var ch; for(i=0; i<len; i++) { ch = num(i); code = code.replace(new RegExp('/b'+dict[i]+'/b','g'), ch); if(ch == dict[i]) dict[i] = ''; } document.getElementById('code').value = "eval(function(p,a,c,k,e,d){e=function(c){return(c<a?'':e(parseInt(c/a)))+((c=c%a)>35?String.fromCharCode(c+29):c.toString(36))};if(!''.replace(/^/,String)){while(c--)d[e(c)]=k[c]||e(c);k=[function(e){return d[e]}];e=function(){return'//w+'};c=1};while(c--)if(k[c])p=p.replace(new RegExp('//b'+e(c)+'//b','g'),k[c]);return p}(" + "'"+code+"',"+a+","+len+",'"+ dict.join('|')+"'.split('|'),0,{}))"; } function num(c) { return(c<a?'':num(parseInt(c/a)))+((c=c%a)>35?String.fromCharCode(c+29):c.toString(36)); } function run() { eval(document.getElementById('code').value); } function decode() { var code = document.getElementById('code').value; code2 = code.replace(/^eval/, ''); //alert(code); document.getElementById('code').value = eval(code2); } <textarea id=code cols=80 rows=20>