javascript中常用函數整理

1.typeof、constructor、instanceof對數組的判斷

代碼如下	複製代碼
var arr = [1,5,6,9,8,5,4]; //var arr = new Array(1,5,6,9,8,5,4); console.log(typeof arr);//object console.log(arr.constructor());//[] console.log(arr instanceof Array);//true

2.函數自調用

代碼如下	複製代碼
(function (a, b) {     console.log(a + b);//30 自調用 })(10, 20);3.去除兩邊空格 function trim (str) {     return str.replace(/^s+|s+$/g, ''); } console.log('   woshi   sss   ');//   woshi   sss   console.log(trim('   woshi   sss   '));//woshi   sss

4.數字判斷

代碼如下	複製代碼
function isNumber(n){     return !isNaN(parseFloat(n)) && isFinite(n); } console.log(isNumber('e345'));

5.數組判斷

代碼如下	複製代碼
function isArray(obj){     return Object.prototype.toString.call(obj) === '[object Array]' ; } console.log(isArray(arr));

6.length的理解

代碼如下	複製代碼
var myArray = [12 , 222 , 1000 ]; myArray.length = 0; // myArray 會變成空數組[].----- length是可讀可寫的屬性

7、base64_encode加密,解密

代碼如下

複製代碼

function base64encode(str){     var out,i,len,base64EncodeChars="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";     var c1,c2,c3;     len=str.length;     i=0;     out="";     while(i<len){         c1=str.charCodeAt(i++)&0xff;         if(i==len){             out+=base64EncodeChars.charAt(c1>>2);             out+=base64EncodeChars.charAt((c1&0x3)<<4);             out+="==";             break;         }         c2=str.charCodeAt(i++);         if(i==len){             out+=base64EncodeChars.charAt(c1>>2);             out+=base64EncodeChars.charAt(((c1&0x3)<<4)|((c2&0xF0)>>4));             out+=base64EncodeChars.charAt((c2&0xF)<<2);             out+="=";             break;         }         c3=str.charCodeAt(i++);         out+=base64EncodeChars.charAt(c1>>2);         out+=base64EncodeChars.charAt(((c1&0x3)<<4)|((c2&0xF0)>>4));         out+=base64EncodeChars.charAt(((c2&0xF)<<2)|((c3&0xC0)>>6));         out+=base64EncodeChars.charAt(c3&0x3F);     }     return out; } function base64decode(str){     var c1,c2,c3,c4,base64DecodeChars=new Array(-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-1,-1,-1,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,-1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1);     var i,len,out;     len=str.length;     i=0;     out="";     while(i<len){         /* c1 */         do{             c1=base64DecodeChars[str.charCodeAt(i++)&0xff];         }while(i<len&&c1==-1);         if(c1==-1) break;         /* c2 */         do{             c2=base64DecodeChars[str.charCodeAt(i++)&0xff];         }while(i<len&&c2==-1);         if(c2==-1) break;         out+=String.fromCharCode((c1<<2)|((c2&0x30)>>4));         /* c3 */         do{             c3=str.charCodeAt(i++)&0xff;             if(c3==61) return out;             c3=base64DecodeChars[c3];         }while(i<len&&c3==-1);         if(c3==-1) break;         out+=String.fromCharCode(((c2&0XF)<<4)|((c3&0x3C)>>2));         /* c4 */         do{             c4=str.charCodeAt(i++)&0xff;             if(c4==61) return out;             c4=base64DecodeChars[c4];         }while(i<len&&c4==-1);         if(c4==-1) break;         out+=String.fromCharCode(((c3&0x03)<<6)|c4);     }     return out; } function utf16to8(str){     var out,i,len,c;     out="";     len=str.length;     for (i=0;i<len;i++){         c=str.charCodeAt(i);         if((c>=0x0001)&&(c<=0x007F)){             out+=str.charAt(i);         } else if(c>0x07FF){             out+=String.fromCharCode(0xE0|((c>>12)&0x0F));             out+=String.fromCharCode(0x80|((c>>6)&0x3F));             out+=String.fromCharCode(0x80|((c>>0)&0x3F));         } else {             out+=String.fromCharCode(0xC0|((c>>6)&0x1F));             out+=String.fromCharCode(0x80|((c>>0)&0x3F));         }     }     return out; } function utf8to16(str){     var out,i,len,c;     var char2,char3;     out="";     len=str.length;     i=0;     while(i<len){         c=str.charCodeAt(i++);         switch (c>>4){         case 0:         case 1:         case 2:         case 3:         case 4:         case 5:         case 6:         case 7:             // 0xxxxxxx             out+=str.charAt(i-1);             break;         case 12:         case 13:             // 110x xxxx   10xx xxxx             char2=str.charCodeAt(i++);             out+=String.fromCharCode(((c&0x1F)<<6)|(char2&0x3F));             break;         case 14:             // 1110 xxxx  10xx xxxx  10xx xxxx             char2=str.charCodeAt(i++);             char3=str.charCodeAt(i++);             out+=String.fromCharCode(((c&0x0F)<<12)|((char2&0x3F)<<6)|((char3&0x3F)<<0));             break;         }     }     return out; }

8、日期時間

getDay函數：返回星期幾，值為0～6，其中0表示星期日，1表示星期一，...，6表示星期六。例： 

代碼如下	複製代碼
function DateDemo()  {  var d, day, x, s = "Today is: ";  var x = new Array("Sunday", "Monday", "Tuesday");  var x = x.concat("Wednesday","Thursday", "Friday");  var x = x.concat("Saturday");  d = new Date();  day = d.getDay();  return(s += x[day]);  }

(3)getHouse函數：返回日期的"小時"部分，值為0～23。例。 

代碼如下	複製代碼
function TimeDemo()  {  var d, s = "The current local time is: ";  var c = ":";  d = new Date();  s += d.getHours() + c;  s += d.getMinutes() + c;  s += d.getSeconds() + c;  s += d.getMilliseconds();  return(s);  }

(4)getMinutes函數：返回日期的"分鐘"部分，值為0～59。見上例。 
(5)getMonth函數：返回日期的"月"部分，值為0～11。其中0表示1月，2表示3月，...，11表示12月。見前面的例子。 
(6)getSeconds函數：返回日期的"秒"部分，值為0～59。見前面的例子。 
(7)getTime函數：返回系統時間。