remove_fake_ifs.js

.js

const fs = require("fs");
const input = fs.readFileSync("test.js").toString().split("\n");

const ifRegex = /^(\s*)if \((.{7}) (===|!==) (.{7})\)( {|)/;
const elseRegex = /^(\s*)(} else {|} else|else {|else)/;

const removeElseBlock = (index, matches) => {
  let spacesCount = matches[1].length;
  // remove "if ... statement"
  if (matches[5] == " {") {
    input.splice(index, 1);
  } else {
    input[index] = input[index].replace(matches[0].substring(spacesCount), "");
  }

  // remove "else"
  for (let j = index + 1; j < input.length; j++) {
    let elseMatches = input[j].match(elseRegex);
    if (elseMatches != null && elseMatches[1].length == spacesCount) {
      if (elseMatches[2] == "else" || elseMatches[2] == "} else") {
        input.splice(j, 1);
      } else if (elseMatches[2] == "else {" || elseMatches[2] == "} else {") {
        let k = j + 1;
        for (; k < input.length; k++) {
          if (input[k].indexOf(" ".repeat(spacesCount) + "}") == 0) break;
        }

        input.splice(j, k - j + 1);
      }

      break;
    }
  }
};

const removeIfBlock = (index, matches) => {
  let spacesCount = matches[1].length;

  let elseStartIndex = index + 1;
  for (; elseStartIndex < input.length; elseStartIndex++) {
    let elseMatches = input[elseStartIndex].match(elseRegex);
    if (elseMatches != null && elseMatches[1].length == spacesCount) {
      if (elseMatches[2] == "else" || elseMatches[2] == "} else") {
        input[elseStartIndex] = input[elseStartIndex].replace(elseMatches[2], "");
        input.splice(index, elseStartIndex - index);
      } else if (elseMatches[2] == "else {" || elseMatches[2] == "} else {") {
        let k = elseStartIndex + 1;
        for (; k < input.length; k++) {
          if (input[k].indexOf(" ".repeat(spacesCount) + "}") == 0) break;
        }

        input.splice(k, 1);
        input.splice(index, elseStartIndex - index + 1);
      }

      break;
    }
  }
};

for (var i = 0; i < input.length; i++) {
  const matches = input[i].match(ifRegex);
  if (matches != null) {
    if (matches[3] == "===") {
      if (matches[2] === matches[4]) removeElseBlock(i, matches);
      else removeIfBlock(i, matches);
    }
    if (matches[3] == "!==") {
      if (matches[2] !== matches[4]) removeElseBlock(i, matches);
      else removeIfBlock(i, matches);
    }
    i--;
  }
}

fs.writeFileSync("out.js", input.join("\n"));