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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 false
12 };
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()) //true
31 alert("2002-02-31 10:10:40".isDateTime()) //false
32 alert("2002-22-31 10:10:40".isDateTime()) //false
33 alert("2002-22-31 30:10:40".isDateTime()) //false
34 */
35
36
37 // 检查 是否以特定的字符串结束
38 String.prototype.startsWith=function(){
39 var _string=this
40 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 true
44 alert("http://www.google.com/".startsWith("https://","file://")) //false
45 alert("abc".startsWith("a")) //true
46 */
47
48
49 // 检查 是否以特定的字符串结束
50 String.prototype.endsWith=function(){
51 var _string=this
52 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:http://www.cnblogs.com/zengwei/archive/2007/03/23/683474.html