I am working with Google documents that contain hundreds of empty paragraphs. I want to remove these blank lines automatically.
In LibreOffice Writer you can use th
I think there has to be a last empty paragraph but this seems to work.
function myFunction() {
  var body = DocumentApp.getActiveDocument().getBody();
  var paras = body.getParagraphs();
  var i = 0;
  for (var i = 0; i < paras.length; i++) {
       if (paras[i].getText() === ""){
          paras[i].removeFromParent()
       }
}
}
                                                                        Adding to Tom's answer and apmouse's comment, here's a revised solution that: 1) prevents removing paragraphs consisting of images or horizontal rules; 2) also removes paragraphs that only contain whitespace.
function removeEmptyParagraphs() {
  var pars = DocumentApp.getActiveDocument().getBody().getParagraphs();
  // for each paragraph in the active document...
  pars.forEach(function(e) {
    // does the paragraph contain an image or a horizontal rule?
    // (you may want to add other element types to this check)
    no_img = e.findElement(DocumentApp.ElementType.INLINE_IMAGE)    === null;
    no_rul = e.findElement(DocumentApp.ElementType.HORIZONTAL_RULE) === null;
    // proceed if it only has text
    if (no_img && no_rul) {
      // clean up paragraphs that only contain whitespace
      e.replaceText("^\\s+$", "")
      // remove blank paragraphs
      if(e.getText() === "") {
        e.removeFromParent();
      }
    }    
  })
}