function compress(str) {
let dict = {},
data = (str + "").split(""),
out = [],
currChar,
phrase = data[0],
code = 256;
for (let i = 1; i < data.length; i++) {
currChar = data[i];
if (dict[phrase + currChar] != null) phrase += currChar;
else {
out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
dict[phrase + currChar] = code;
code++;
phrase = currChar;
}
}
out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
for (let i = 0; i < out.length; i++) out[i] = String.fromCharCode(out[i]);
return out.join("");
}
function decompress(str) {
let dict = {},
data = (str + "").split(""),
currChar = data[0],
oldPhrase = currChar,
out = [currChar],
code = 256,
phrase;
for (let i = 1; i < data.length; i++) {
let currCode = data[i].charCodeAt(0);
if (currCode < 256) phrase = data[i];
else phrase = dict[currCode] ? dict[currCode] : (oldPhrase + currChar);
out.push(phrase);
currChar = phrase.charAt(0);
dict[code] = oldPhrase + currChar;
code++;
oldPhrase = phrase;
}
return out.join("");
}
const fetch = require('node-fetch');
fetch('https://gist.githubusercontent.com/SiddharthShyniben/29293ad446d94b7d972448943159ccae/raw/5a0fcfcd8052a27d6ae93954dbbf97b6ccfd61a4/image.txt')
.then(res => res.text())
.then(data => console.log({
original: data,
originalLength: data.length,
compressed: compress(data),
compressedLength: compress(data).length,
diff: data.length - compress(data).length,
diffPercentage: (((data.length - compress(data).length) / data.length) * 100) + "%",
compressionWorks: data === decompress(compress(data))
}))
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