Update Bibliography Google Docs Documents

/***
 * A script which updates the bibliography numbering if there are some extra recorrd.
 * For example if you have added extra [2.1] and [4.1], the script will 
 * go trhou it and will make [2.1] to [3] and [4.1] to [5], because [4] is already [5]
 * The script will print the mapping as well.
 **/
function updateBibliography() {
  var bodyElement = DocumentApp.getActiveDocument().getBody();
//initial max number or reference, to generate the mapping  
  var max = 30;
  var arr = [];
  for(var i = 1; i <= max; i++) {
    arr.push("\\["+i+"\\]");
  }
  //add the extra bibliography recorrds, which should be mapped
  arr.splice(4, 0, "\\[4.1\\]","\\[4.2\\]");
  
  var correct = [];
  max = arr.length;
  //generation of the bibliography mapping
  for(i = 1; i <= max; i++) {
    correct.push("\["+i+"\]");
  }
  var output = '';
  for(i = arr.length - 1; i >= 0; i--) {
    bodyElement.replaceText(arr[i], correct[i]);
    output += arr[i] + '=>' + correct[i] + '\n'; 
  }
  
  DocumentApp.getUi().alert(output);
}

A handy Google App script which updates the bibliography numbering in a scientific document