javascript常用函数归纳整理

本文整理归纳了一些js常用函数，其中包括对数据操作，字符替换操作，日期及加解密操作函数，还有一些简单的验证函数。便于大家查阅参考。相信对大家会有所帮助。

1.typeof、constructor、instanceof对数组的判断

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.函数自调用

(function (a, b) {

    console.log(a + b);//30 自调用

})(10, 20);3.去除两边空格

function trim (str) {

    return str.replace(/^s+|s+$/g, '');

}

console.log('   woshi   sss   ');//   woshi   sss   

console.log(trim('   woshi   sss   '));//woshi   sss

4.数字判断

function isNumber(n){

    return !isNaN(parseFloat(n)) && isFinite(n);

}

console.log(isNumber('e345'));

5.数组判断

function isArray(obj){

    return Object.prototype.toString.call(obj) === '[object Array]' ;

}

console.log(isArray(arr));

6.length的理解

var myArray = [12 , 222 , 1000 ];

myArray.length = 0; // myArray 会变成空数组[].----- length是可读可写的属性

7、base64_encode加密,解密

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、日期时间
getDay函数：返回星期几，值为0～6，其中0表示星期日，1表示星期一，...，6表示星期六。例：

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函数：返回日期的"小时"部分，值为0～23。例。

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函数：返回日期的"分钟"部分，值为0～59。见上例。 
(5)getMonth函数：返回日期的"月"部分，值为0～11。其中0表示1月，2表示3月，...，11表示12月。见前面的例子。 
(6)getSeconds函数：返回日期的"秒"部分，值为0～59。见前面的例子。 
(7)getTime函数：返回系统时间。

希望本文所述对大家的javascript程序设计有所帮助。