JavaScript代码优化实战之一：缓存变量，关键字过滤
无意中看到某网站的一段JS代码：
1 function clearSearchText(){ 2 var searchtext = document.getElementById("searchwordl").value 3 document.getElementById("searchwordl").value=""; 4 } 5 function replaceALL(){ 6 var replaceTxt = document.getElementById("searchwordl").value; 7 var relTxt = replaceTxt.replace(/^\s+|\s+$/g,""); 8 if(typeof(document.getElementById("searchwordl"))=="undefined"||relTxt==""){ 9 alert("请输入检索条件");10 document.getElementById("searchwordl").focus();11 return false;12 }13 if(typeof(document.getElementById("searchwordl"))!="undefined"){14 var searchwordl = document.getElementById('searchwordl').value;15 16 var sig = 0;17 if(searchwordl.indexOf("'") > -1 || searchwordl.indexOf("\"") > -1 || searchwordl.indexOf("%") > -1 || searchwordl.indexOf("#") > -1 || searchwordl.indexOf("&") > -1 || searchwordl.indexOf("*") > -1 || searchwordl.indexOf("(") > -1 || searchwordl.indexOf(")") > -1 || searchwordl.indexOf("@") > -1 || searchwordl.indexOf("`") > -1 || searchwordl.indexOf("/") > -1 || searchwordl.indexOf("\\") > -1 || searchwordl.indexOf(",") > -1 || searchwordl.indexOf(".") > -1 || searchwordl.indexOf("=") > -1 || searchwordl.indexOf("<") > -1 || searchwordl.indexOf(">") > -1)18 sig = 1;19 20 searchwordl=searchwordl.replace("'",""); 21 //searchwordl=searchwordl.replace(" ","");22 searchwordl=searchwordl.replace("%","");23 searchwordl=searchwordl.replace("#","");24 searchwordl=searchwordl.replace("&","");25 searchwordl=searchwordl.replace("*","");26 searchwordl=searchwordl.replace("(","");27 searchwordl=searchwordl.replace(")","");28 searchwordl=searchwordl.replace("@","");29 searchwordl=searchwordl.replace("`","");30 searchwordl=searchwordl.replace("/","");31 searchwordl=searchwordl.replace("\\","");32 searchwordl=searchwordl.replace(",","");33 searchwordl=searchwordl.replace(".","");34 searchwordl=searchwordl.replace("=","");35 searchwordl=searchwordl.replace("<","");36 searchwordl=searchwordl.replace(">","");37 if(searchwordl == '请输入搜索条件'){38 alert("请输入搜索条件");39 return false;40 }41 if(searchwordl == ''){42 alert("请正确输入搜索条件");43 return false;44 }45 if(sig == 1){46 alert("请正确输入搜索条件");47 return false;48 }49 document.getElementById('searchword').value=searchwordl;50 return true;51 //document.fmsearch.submit();52 }53 }场景是网页上有一个搜索框，输入框的onfocus事件调用了clearSearchText方法，提交前调用了replaceALL方法。
以上代码主要存在以下问题：
1、逻辑不对：onfocus事件直接把内容清空是不合理的。
2、常用到的变量没有缓存：多次用到了document.getElementById("searchwordl")
3、变量没有集中声明
4、JavaScript中的replace方法只替换一次，上面的代码中原意应该是全部替换
5、代码臃肿
由于最近正在看JavaScript代码优化方面的书，所以一时手痒就对这段代码进行了一个优化，现在分享出来，欢迎大家点评。
function clearSearchText(){ var search=document.getElementById("searchwordl"); search.value= search.value == search.defaultValue ? "":search.value;}function replaceALL(){ var search=document.getElementById("searchwordl"), searchword = search.value.replace(/ /g,""); if(searchword == ""){ alert("请输入检索条件"); search.focus(); return false; } searchword=searchword.replace(/['%#&\*\(\)@`\/\\,\.=<>]/g,""); if(searchword == search.defaultValue || searchword == ''){ alert("请正确输入搜索条件"); search.focus(); return false; } search.value=searchword; return true;}另外，页面中用了jQuery，所以上面的代码如果用jQuery会更简洁。
欢迎大家给出更好的优化方案。
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