以下为web开发中常用到的js方法；收集并整理出来；简单的就不写出来了 
// 返回字符的长度，一个中文算2个 String.prototype.ChineseLength = function ()
{ 
return this.replace(/[^\x00-\xff]/g,"**").length;
} // 判断字符串是否以指定的字符串结束 String.prototype.EndsWith = function (str) { return this.substr(this.length - str.length) == str;} // 去掉字符左端的的空白字符 String.prototype.LeftTrim = function () { return this.replace(/(^[\\s]*)/g, "");} // 去掉字符右端的空白字符 String.prototype.RightTrim = function () { return this.replace(/([\\s]*$)/g, "");} // 判断字符串是否以指定的字符串开始 String.prototype.StartsWith = function (str) { return this.substr(0, str.length) == str;} // 去掉字符两端的空白字符 String.prototype.Trim = function () { return this.replace(/(^\s*)|(\s*$)/g, "");}
1 <! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > 2 < HTML > 3 < HEAD > 4 < TITLE > New Document </ TITLE > 5 < META NAME ="Generator" CONTENT ="EditPlus" > 6 < META NAME ="Author" CONTENT ="" > 7 < META NAME ="Keywords" CONTENT ="" > 8 < META NAME ="Description" CONTENT ="" > 9 < script language =javascript > 10 String.prototype.Replace = function(oldValue,newValue) 11
{ 12 var reg = new RegExp(oldValue,"g"); 13 return this.replace(reg, newValue); 14
}15 //字符串替换；曾经很头疼写了很多代码，还是这个简单16 function replace(obj)17 { 18 alert(obj.value.Replace("a","d"));19 }2021 // 另存为文件22 function SaveCode(obj, filename) 23 { 24 var win = window.open('', '_blank', 'top=100'); 25 var code = obj.innerText; 26 code = code == null || code == "" ? obj.value : code; 27 win.opener = null;28 win.document.write(code);29 win.document.execCommand('saveas', true, filename);30 win.close();31 }32 // 问候33 window.onload = function()34 { 35 var now = new Date();36 var hour = now.getHours();37 var greeting;38 if (hour < 6)39 greeting = "凌晨好";40 else if (hour < 10)41 greeting = "早上好";42 else if (hour < 14)43 greeting = "中午好";44 else if (hour < 18)45 greeting = "下午好";46 else 47 greeting = "晚上好";48 49 document.getElementById("hi").innerHTML = "<font color=red>" + greeting + "</font>" ;50 }51 // 将光标停在对象的最后52 function PutCursorAtLast(obj) 53 { 54 obj.focus();55 var range = obj.createTextRange(); 56 range.moveStart('character',obj.value.length); 57 range.collapse(true); 58 range.select(); 59 }60 // 将光标停在对象的最前61 function PutCursorAtFirst(obj) 62 { 63 obj.focus();64 var range = obj.createTextRange(); 65 range.moveStart('character',0); 66 range.collapse(true); 67 range.select(); 68 }69 </ script > 70 </ HEAD > 71 72 < BODY > 73 < span id ="hi" ></ span > 74 < br /> 75 < span > curssor at last </ span > 76 < br /> 77 < input type =text value ="curssor at last" onclick =PutCursorAtLast(this) > 78 < br /> 79 < span > curssor at first </ span > 80 < br /> 81 < input type =text value ="curssor at first" onclick =PutCursorAtFirst(this) > 82 < br /> 83 < span > String.Replace </ span > 84 < br /> 85 < INPUT TYPE =TEXT value ="replace" ONCLICK =replace(this) > 86 < br /> 87 < span > save file </ span > 88 < br /> 89 < input type =text value ="hello word" onclick =SaveCode(this,"save") > 90 </ BODY > 91 </ HTML > 92
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > 2 < HTML > 3 < HEAD > 4 < TITLE > New Document </ TITLE > 5 < META NAME ="Generator" CONTENT ="EditPlus" > 6 < META NAME ="Author" CONTENT ="" > 7 < META NAME ="Keywords" CONTENT ="" > 8 < META NAME ="Description" CONTENT ="" > 9 < script language =javascript > 10 String.prototype.Replace = function(oldValue,newValue) 11 { 12 var reg = new RegExp(oldValue,"g"); 13 return this.replace(reg, newValue); 14 }15 //字符串替换；曾经很头疼写了很多代码，还是这个简单16 function replace(obj)17 { 18 alert(obj.value.Replace("a","d"));19 }2021 // 另存为文件22 function SaveCode(obj, filename) 23 { 24 var win = window.open('', '_blank', 'top=100'); 25 var code = obj.innerText; 26 code = code == null || code == "" ? obj.value : code; 27 win.opener = null;28 win.document.write(code);29 win.document.execCommand('saveas', true, filename);30 win.close();31 }32 // 问候33 window.onload = function()34 { 35 var now = new Date();36 var hour = now.getHours();37 var greeting;38 if (hour < 6)39 greeting = "凌晨好";40 else if (hour < 10)41 greeting = "早上好";42 else if (hour < 14)43 greeting = "中午好";44 else if (hour < 18)45 greeting = "下午好";46 else 47 greeting = "晚上好";48 49 document.getElementById("hi").innerHTML = "<font color=red>" + greeting + "</font>" ;50 }51 // 将光标停在对象的最后52 function PutCursorAtLast(obj) 53 { 54 obj.focus();55 var range = obj.createTextRange(); 56 range.moveStart('character',obj.value.length); 57 range.collapse(true); 58 range.select(); 59 }60 // 将光标停在对象的最前61 function PutCursorAtFirst(obj) 62 { 63 obj.focus();64 var range = obj.createTextRange(); 65 range.moveStart('character',0); 66 range.collapse(true); 67 range.select(); 68 }69 </ script > 70 </ HEAD > 71 72 < BODY > 73 < span id ="hi" ></ span > 74 < br /> 75 < span > curssor at last </ span > 76 < br /> 77 < input type =text value ="curssor at last" onclick =PutCursorAtLast(this) > 78 < br /> 79 < span > curssor at first </ span > 80 < br /> 81 < input type =text value ="curssor at first" onclick =PutCursorAtFirst(this) > 82 < br /> 83 < span > String.Replace </ span > 84 < br /> 85 < INPUT TYPE =TEXT value ="replace" ONCLICK =replace(this) > 86 < br /> 87 < span > save file </ span > 88 < br /> 89 < input type =text value ="hello word" onclick =SaveCode(this,"save") > 90 </ BODY > 91 </ HTML > 92 // 返回字符的长度，一个中文算2个 String.prototype.ChineseLength = function () { return this.replace(/[^\x00-\xff]/g,"**").length;} // 判断字符串是否以指定的字符串结束 String.prototype.EndsWith = function (str) { return this.substr(this.length - str.length) == str;} // 去掉字符左端的的空白字符 String.prototype.LeftTrim = function () { return this.replace(/(^[\\s]*)/g, "");} // 去掉字符右端的空白字符 String.prototype.RightTrim = function () { return this.replace(/([\\s]*$)/g, "");} // 判断字符串是否以指定的字符串开始 String.prototype.StartsWith = function (str) { return this.substr(0, str.length) == str;} // 去掉字符两端的空白字符 String.prototype.Trim = function () { return this.replace(/(^\s*)|(\s*$)/g, "");} 都是基于 String.prototype 的扩展:
起因是有个网友和我讨论两个函数，
一个是 isDateTime (判断字符是否是符合 yyyy-mm-dd hh:mm:ss日期格式)另一个是 left 函数，类似vbscript的left 实现中英文字符的混合截取。他两个函数都用了循环，还用了N多 if 语句，每个函数都超过了40行代码，问我有无好的办法精简一下。于是，我就写出了下面的代码，不敢说最效率最高，但是已经是够精简了， left函数才1行 1 <script type="text/javascript"> 2 3 //by Go_Rush(阿舜) from http://ashun.cnblogs.com/ 4 5 function $A(arrayLike){ 6 for(var i=0,ret=[];i<arrayLike.length;i++) ret.push(arrayLike[i]) 7 return ret 8 }; 9 Array.prototype.any=function(f){ 10 for(var i=0;i<this.length;i++) if (f(this[i],i,this)) return true;11 return false12 };13 14 15 16 //判断 字符串 是否符合 yyyy-mm-dd hh:mm:ss的日期格式, 格式正确而且闰年闰月等也要正确17 18 String.prototype.isDateTime=function(){ 19 try{ 20 var arr=(this.length==19)?this.split(/\D/):[]21 --arr[1]22 eval("var d=new Date("+arr.join(",")+")") 23 return Number(arr[0])==d.getFullYear() && Number(arr[1])==d.getMonth() 24 && Number(arr[2])==d.getDate() && Number(arr[3])==d.getHours()25 && Number(arr[4])==d.getMinutes() && Number(arr[5])==d.getSeconds()26 }catch(x){ return false}27 }28 29 /*30 alert("2002-12-12 10:10:40".isDateTime()) //true31 alert("2002-02-31 10:10:40".isDateTime()) //false32 alert("2002-22-31 10:10:40".isDateTime()) //false33 alert("2002-22-31 30:10:40".isDateTime()) //false34 */35 36 37 // 检查 是否以特定的字符串结束38 String.prototype.startsWith=function(){ 39 var _string=this40 return $A(arguments).any(function(value){ return _string.slice(0,value.length)==value})41 };42 /*43 alert("http://www.google.com/".startsWith("http://","ftp://","telnet://")) //true 满足其中任何一个就返回 true44 alert("http://www.google.com/".startsWith("https://","file://")) //false45 alert("abc".startsWith("a")) //true46 */47 48 49 // 检查 是否以特定的字符串结束50 String.prototype.endsWith=function(){ 51 var _string=this52 return $A(arguments).any(function(value){ return _string.slice(value.length*(-1))==value})53 };54 55 56 57 //从左边截取n个字符 ,如果包含汉字,则汉字按两个字符计算58 String.prototype.left=function(n){ 59 return this.slice(0,n-this.slice(0,n).replace(/[\x00-\xff]/g,"").length)60 };61 /*62 alert("abcdefg".left(3)==="abc")63 alert("中国人cdefg".left(5)==="中国")64 alert("中国abcdefg".left(5)==="中国a")65 */66 67 68 69 70 //从右边截取n个字符 ,如果包含汉字,则汉字按两个字符计算71 String.prototype.right=function(n){ 72 return this.slice(this.slice(-n).replace(/[\x00-\xff]/g,"").length-n)73 };74 75 /*76 alert("abcdefg".right(3)==="efg")77 alert("cdefg中国人".right(5)==="国人")78 alert("abcdefg中国".right(5)==="g中国")79 */80 81 </script>来源：