無意中看到某網站的一段JS代碼：
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("請輸入檢索條件"); 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 == '請輸入搜索條件'){ 38 alert("請輸入搜索條件"); 39 return false; 40 } 41 if(searchwordl == ''){ 42 alert("請正確輸入搜索條件"); 43 return false; 44 } 45 if(sig == 1){ 46 alert("請正確輸入搜索條件"); 47 return false; 48 } 49 document.getElementById('searchword').value=searchwordl; 50 return true; 51 //document.fmsearch.submit(); 52 } 53 }
場景是網頁上有一個搜索框，輸入框的onfocus事件調用了clearSearchText方法，提交前調用了replaceALL方法。
以上代碼主要存在以下問題：
1、邏輯不對：onfocus事件直接把內容清空是不合理的。
2、常用到的變量沒有緩存：多次用到了document.getElementById("searchwordl")
3、變量沒有集中聲明
4、JavaScript中的replace方法只替換一次，上面的代碼中原意應該是全部替換
5、代碼臃腫
由於最近正在看JavaScript代碼優化方面的書，所以一時手癢就對這段代碼進行了一個優化，現在分享出來，歡迎大家點評。
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("請輸入檢索條件"); search.focus(); return false; } searchword=searchword.replace(/['%#&\*\(\)@`\/\\,\.=<>]/g,""); if(searchword == search.defaultValue || searchword == ''){ alert("請正確輸入搜索條件"); search.focus(); return false; } search.value=searchword; return true; }
另外，頁面中用了jQuery，所以上面的代碼如果用jQuery會更簡潔。
歡迎大家給出更好的優化方案。