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JavaScript

var enc = '1010101011101100100010100011011111101010010110010100100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000';

console.log(enc);

var dec;
console.log(
    dec = 
    // Encode
    enc.match(/.{1,6}/g).map(function(chunk, idx, arr) {
        return [Math.min(61, parseInt(chunk, 2)), (this.rem = Math.max(0, (parseInt(chunk, 2) + this.rem || 0) - 62)) > 0 && idx == arr.length - 1 ? this.rem : -1].map(function(n) {
            return "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".charAt(n)
        }).join('')
    }).join('')
);
console.log("toto");
console.log(
    // Decode
    dec.split('').reverse().map(function(chr) {
        var s = "000000" +  "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".indexOf(chr).toString(2);
        return s.substr(s.length - 6);
    }).reverse().join('')
);