String 類別是最常用的類別,但在 javascript 中並非提供基本函式,像是 substr(), trim(), startsWith() 等,這篇文章示範如何實作 Javascript String 類別的 buildin 函式
myVar = substr2(myVar, x, y); //Your function
myVar = myVar.substr(x, y); //built-in function
Trim()
String.prototype.trim = function(){return
(this.replace(/^[\s\xA0]+/, "").replace(/[\s\xA0]+$/, ""))}
startsWith()
String.prototype.startsWith = function(str)
{return (this.match("^"+str)==str)}
endsWith()
String.prototype.startsWith = function(str)
{return (this.match("^"+str)==str)}
接著就可以用 build-in 的方式,呼叫這幾個函式
var myStr = "Earth is a beautiful planet";
var myStr2 = myStr.trim();
//=="Earth is a beautiful planet";
if (myStr2.startsWith("Earth")) // returns TRUE
if (myStr2.endsWith("planet")) // returns TRUE
if (myStr.startsWith("Earth"))
// returns FALSE due to the leading spaces…
if (myStr.endsWith("planet"))
// returns FALSE due to trailing spaces…