Encode into Base64

btoa.js

function btoa(
    a, //String to encode
    b, //Array of Base64 characters
    c,d,e,f,g,x //Placeholder
    ){
    for(d=a.length, //Set d to the input's length
        e="charCodeAt", //Shortcut for String.charCodeAt
        f=-[,2,1][d%3], //Get how many equal signs need to be added to the end
        x=0; //Initiate iteration variable
        x<d; //Continue loop until x exceeds the length of the input
    )
    g=a[e](x++)<<16|a[e](x++)<<8|a[e](x++), //Create a binary buffer of the three characters at x, while incrementing x by 3
    c=[c]+b[g>>18&63]+b[g>>12&63]+b[g>>6&63]+b[g&63]; //Push the 4 characters described by that buffer to the returned buffer
    return f?c.slice(0,f)+(~f?"==":"="):c;
}