minify2.js

var chars = 'abcdefghijklmopquwxyz';

//var c = ['block_sss', 'elem__asdf', 'footer__container', 'title', 'title__child','title__child','title__child','title__child'];
var parts = [];

function minify(classNames) {
  var names = [];

  for (var i = 0; i < classNames.length; i++) {
    var className = classNames[i];

    if (names[className]) {
      names[className]++;
    } else {
      names[className] = 1;
    }
  }

  var max = 0;
  var namesByCount = {};

  for (var name in names) {
    var count = names[name];
    max = Math.max(max, count);

    var key = count.toString();
    if (namesByCount[key]) {
      namesByCount[key].push(name);
    } else {
      namesByCount[key] = [name];
    }
  }

  var sortedClassNames = [];

  for (var i = max; i > 0; i--) {
    var key = i.toString();
    if (namesByCount[key]) {
      sortedClassNames = sortedClassNames.concat(namesByCount[key]);
    }
  }

  // here we got array of classes, sorted by number of their appearance

  var minifiedNames = {};

  for (var i = 0; i < sortedClassNames.length; i++) {
    var className = sortedClassNames[i];
    var minifiedName = getMinifiedName();

    minifiedNames[className] = minifiedName;
  }

  //console.log(minifiedNames);

  return minifiedNames;
}

function getMinifiedName() {

  var lastPartIndex = parts.length - 1;

  function incPart(index) {
    var part = parts[index];
    if (!part) {
      for (var i = 0; i <= lastPartIndex + 1; i++) {
        parts[i] = 'a';
      }
    } else {
      var i = chars.indexOf(part);
      i++;
      if (i === chars.length) {
        parts[index] = 'a';
        incPart(index - 1);
      } else {
        parts[index] = chars[i];
      }
    }
  }

  incPart(lastPartIndex);

  return parts.join('');
}

module.exports = minify;