[ 자바스크립트 ] window.atob() & window.btoa()

정확한 사용 용도는 모르지만, 일단 퍼놓기... ─.─;;

 
[ 네이버 지식백과 ] 

encode : 
암호로 바꾸다. 부호화하다. 입력된 데이터를 컴퓨터 속에서 사용하는 코드로 변환하다. 

decode : 
(암호를) 해독하다. 코드(부호)화된 데이터를 원래 형태로 변환하다. 
어떤 규칙에 따라 부호로 변환된 데이터를 원래 형태로 되돌리다. 
 

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<script type="text/javascript">
/* 
 * window.atob() 함수가 적용되지 않을 때 추가할 내용 ( ie 9 이하 ) 
 * 출처 : http://www.webtoolkit.info/javascript-base64.html 
*/ 

( function (){ 
    if ( ! window.atob ){ 

        window.atob = function ( b64text ){  return Base64.decode( b64text );  }; 
        window.btoa = function ( utf8text ){  return Base64.encode( utf8text );  }; 

        var Base64 = { 

            keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=", 


            encode : function ( input ){ 
                var output = ""; 
                var chr1, chr2, chr3, enc1, enc2, enc3, enc4; 
                var x = 0; 

                input = Base64._utf8_encode( input ); 

                while ( x < input.length ){ 

                    chr1 = input.charCodeAt( x++ ); 
                    chr2 = input.charCodeAt( x++ ); 
                    chr3 = input.charCodeAt( x++ ); 

                    enc1 = chr1 >> 2; 
                    enc2 = ((chr1 & 3) << 4) | (chr2 >> 4); 
                    enc3 = ((chr2 & 15) << 2) | (chr3 >> 6); 
                    enc4 = chr3 & 63; 

                    if ( isNaN(chr2) ) enc3 = enc4 = 64; 
                    else if ( isNaN(chr3) ) enc4 = 64; 

                    output = output + this.keyStr.charAt( enc1 ) + this.keyStr.charAt( enc2 ) + this.keyStr.charAt( enc3 ) + 
                                this.keyStr.charAt( enc4 ); 
                } 

                return output; 
            }, 


            decode : function ( input ){ 
                var output = ""; 
                var chr1, chr2, chr3; 
                var enc1, enc2, enc3, enc4; 
                var x = 0; 

                input = input.replace( /[^A-Za-z0-9\+\/\=]/g , "" ); 

                while ( x < input.length ){ 

                    enc1 = this.keyStr.indexOf( input.charAt(x++) ); 
                    enc2 = this.keyStr.indexOf( input.charAt(x++) ); 
                    enc3 = this.keyStr.indexOf( input.charAt(x++) ); 
                    enc4 = this.keyStr.indexOf( input.charAt(x++) ); 

                    chr1 = (enc1 << 2) | (enc2 >> 4); 
                    chr2 = ((enc2 & 15) << 4) | (enc3 >> 2); 
                    chr3 = ((enc3 & 3) << 6) | enc4; 

                    output = output + String.fromCharCode( chr1 ); 

                    if ( enc3 != 64 ) output = output + String.fromCharCode( chr2 ); 

                    if ( enc4 != 64 ) output = output + String.fromCharCode( chr3 ); 
                } 

                output = Base64._utf8_decode( output ); 

                return output; 
            }, 


            _utf8_encode : function ( string ){ 
                string = string.replace( /\r\n/g , "\n" ); 
                var utftext = ""; 

                for ( var n = 0; n < string.length; n++ ){ 

                    var c = string.charCodeAt( n ); 

                    if ( c < 128 ) utftext += String.fromCharCode( c ); 

                    else if ( (c > 127) && (c < 2048) ){ 
                        utftext += String.fromCharCode( (c >> 6) | 192 ); 
                        utftext += String.fromCharCode( (c & 63) | 128 ); 
                    } 

                    else { 
                        utftext += String.fromCharCode( (c >> 12) | 224 ); 
                        utftext += String.fromCharCode( ( (c >> 6) & 63 ) | 128 ); 
                        utftext += String.fromCharCode( (c & 63) | 128 ); 
                    } 
                } 

                return utftext; 
            }, 


            _utf8_decode : function ( utftext ){ 
                var string = ""; 
                var x = 0; 
                var c = c1 = c2 = 0; 

                while ( x < utftext.length ){ 

                    c = utftext.charCodeAt( x ); 

                    if ( c < 128 ) { 
                        string += String.fromCharCode( c ); 
                        x++; 
                    } 

                    else if ( (c > 191) && (c < 224) ){ 
                        c2 = utftext.charCodeAt( x + 1 ); 
                        string += String.fromCharCode( ( (c & 31) << 6 ) | (c2 & 63) ); 
                        x += 2; 
                    } 

                    else { 
                        c2 = utftext.charCodeAt( x + 1 ); 
                        c3 = utftext.charCodeAt( x + 2 ); 
                        string += String.fromCharCode( ( (c & 15) << 12 ) | ( (c2 & 63) << 6 ) | (c3 & 63) ); 
                        x += 3; 
                    } 
                } 

                return string; 
            } 
        } 
    } 
}() ); 
</script>
 

---

enc :  
dec :  

 

<button onclick="testing()"> 클릭하세요 </button><br />

enc : <span id="demo1"> </span><br />
dec : <span id="demo2"> </span>

<script type="text/javascript">

function testing (){ 

        var string = "Hi, everyone!"; 

        var enc = btoa( string ); 
        var dec = atob( enc ); 

        demo1.innerHTML = enc; 
        demo2.innerHTML = dec; 
} 
</script>