文字列を Base64 にエンコードする. JavaScript

btoa() を使用して文字列を Base64 にエンコードする

JavaScript

Output result

TGVhcm5pbmcgSmF2YVNjcmlwdA==
Learning JavaScript

Base64 オブジェクトを使用して文字列を Base64 にエンコードする

JavaScript

const Base64 = {

_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

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

input = Base64._utf8_encode(input);

while (i < input.length) {

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

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 +
        Base64._keyStr.charAt(enc1) + Base64._keyStr.charAt(enc2) +
        Base64._keyStr.charAt(enc3) + Base64._keyStr.charAt(enc4);

}

return output;
},

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

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

while (i < input.length) {

enc1 = Base64._keyStr.indexOf(input.charAt(i++));
        enc2 = Base64._keyStr.indexOf(input.charAt(i++));
        enc3 = Base64._keyStr.indexOf(input.charAt(i++));
        enc4 = Base64._keyStr.indexOf(input.charAt(i++));

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");
    let utftext = "";

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

let 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) {
    let string = "";
    let i = 0;
    let c = c1 = c2 = 0;

while ( i < utftext.length ) {

c = utftext.charCodeAt(i);

if (c < 128) {
            string += String.fromCharCode(c);
            i++;
        }
        else if((c > 191) && (c < 224)) {
            c2 = utftext.charCodeAt(i+1);
            string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
            i += 2;
        }
        else {
            c2 = utftext.charCodeAt(i+1);
            c3 = utftext.charCodeAt(i+2);
            string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
            i += 3;
        }

}
    return string;
}
}

const string = 'Learning JavaScript';

const encodedString = Base64.encode(string);
console.log(encodedString);

const decodedString = Base64.decode(encodedString);
console.log(decodedString);

Output result

TGVhcm5pbmcgSmF2YVNjcmlwdA==
Learning JavaScript.

JavaScript

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文字列を Base64 にエンコードする. JavaScript

JavaScript

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