Algorithm

  1. Input:

    • Accept the input string that needs to be encoded.

  2. Character to ASCII:

    • Iterate through each character in the input string.
    • Convert each character to its ASCII value.

  3. ASCII to Binary:

    • Convert each ASCII value to its binary representation.

  4. Grouping into 6-bit chunks:

    • Group the binary representation into chunks of 6 bits.

  5. Padding:

    • If the length of the binary representation is not a multiple of 6, add zero bits to the right until it is.

  6. Conversion to Decimal:

    • Convert each 6-bit binary chunk to its decimal equivalent.

  7. Base64 Mapping:

    • Map each decimal value to the corresponding Base64 character using the Base64 character set.

  8. Concatenation:

    • Concatenate the Base64 characters to form the final encoded string.

 

Code Examples

#1 Code Example- Encode a String to Base64 Using btoa()

Code - Javascript Programming

// program to encode a string to Base64
// defining the string
const str = "Learning JavaScript"; 

// encoding the string
const result = window.btoa(str);
console.log(result);

// decoding the string
const result1 = window.atob(result);
console.log(result1);
Copy The Code & Try With Live Editor

Output

x
–
+
cmd
TGVhcm5pbmcgSmF2YVNjcmlwdA==
Learning JavaScript

#2 Code Example- Encode a String to Base64 Using Base64 Object

Code - Javascript Programming

// program to encode a string to Base64
// create Base64 Object
const Base64 = {
// private property
_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

// public method for encoding
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;
},

// public method for decoding
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;

},

// private method for UTF-8 encoding
_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;
},

// private method for UTF-8 decoding
_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;
}
}

// define the string
const string = 'Learning JavaScript';

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

// decode the String
const decodedString = Base64.decode(encodedString);
console.log(decodedString>;
Copy The Code & Try With Live Editor

Output

x
–
+
cmd
TGVhcm5pbmcgSmF2YVNjcmlwdA==
Learning JavaScript.
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Demonstration

JavaScript Program Example to Encode a String to Base64-DevsEnv

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