base64_encoder.js

base64_encode.js

const base64_chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' +
    'abcdefghijklmnopqrstuvwxyz' +
    '0123456789+/';

const base64_encode = (input) => {  
    let length = input.length;
    
    let [i, j, k, s] = [0, 0, 0, 0];
  
    let char_array_3 = new Array(3);
    let char_array_4 = new Array(4);

    const b64len = (length+2 - ((length+2) % 3)) * 4 / 3;
    const b64str = new Array(b64len + 1);    
    
    while (length--) {
        char_array_3[i++] = input[k++];
        if (i == 3) {
            char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
            char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
            char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
            char_array_4[3] = char_array_3[2] & 0x3f;

            for (i = 0; i < 4; i++)
                b64str[s++] = base64_chars[char_array_4[i]];

            i = 0;
        }
    }
    if (i) {
        for (j = i; j < 3; j++)
            char_array_3[j] = '\0';

        char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
        char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
        char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
        char_array_4[3] = char_array_3[2] & 0x3f;

        for (j = 0; j < i + 1; j++)
            b64str[s++] = base64_chars[char_array_4[j]];

        while (i++ < 3)
            b64str[s++] = '=';
    }

    return b64str.join('');
}

let _btoa = str => {
  return base64_encode(str.split('').map(c => c.charCodeAt(0)));
}

console.log(_btoa(document.location.href));
console.log(btoa(document.location.href));