Question 296996 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – Compress lowercase string into mixed case

How can I compress strings such that :

  • input is lowercase alphanumeric and the dot character
  • output must be alphanumeric mixed case only

The input is short and has no repetition

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2

Answers


  1. 0

    Something like this could work if I understand it correctly:

    const compressString = (input) => {
    if (!/^[a-z0-9.]+$/.test(input)) {
        throw new Error("Invalid input: must be lowercase alphanumeric and dots only");
    }

    const dotReplacement = 'Z';

    const result = input.replace(/./g, dotReplacement).toUpperCase();

    return result;
}

const input = "example.string";
const compressed = compressString(input);
console.log(compressed);

    To be honest this is probably very basic example but you can use it as start I guess.

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  2. 0

    Your input can contain 37 different characters (lowercase letters, digits, dot), which can be expressed with 6 bits per character.

    Your output can contain 62 different characters (upper- and lowercase letters and digits), which suggests a base62 encoding.

    const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

function compress(input) {
  input = input.toUpperCase();
  var int = 0;
  for (var i = 0; i < input.length; i++) {
    code = input.charCodeAt(i) - 48;
    if (code === -2) code = 50 // special value for .
    int = (int << 6) + code;
  }
  var res = "";
  while (int > 0) {
    res = alphabet[int % 62] + res;
    int = Math.floor(int / 62);
  }
  return res;
}
    Input: <input onchange="out.value = compress(this.value)"><br>
Output: <input id="out" readonly/>

    A corresponding decoding function can also be written.

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