Regex in textreplace google app script is not working - regex

Question

Trying to replace text + date just by date using regex, but it not works:
function myfunction() {
var SourceFolder = DriveApp.getFolderById("");
var Files = SourceFolder.getFiles()
var body = DocumentApp.getActiveDocument().getBody();
while(Files.hasNext()) {
var file = Files.next();
body.replaceText("Date: \d{2}.\d{2}.\d{4}", "31.10.2020")
}
}
Thanks

Answer 1

In your code, var body = DocumentApp.getActiveDocument().getBody(); is declared outside of the loop, so you always refer to the active document body in your while loop.
You may use
while(Files.hasNext()) {
var file = Files.next();
var doc = DocumentApp.openById(file.getId());
var body = doc.getBody();
body.replaceText("Date: \\d{2}\\.\\d{2}\\.\\d{4}", "31.10.2020")
}
The point here is to use double backslashes in the pattern, and escape the dot chars since otherwise a . matches any char but a line break char.

Answer 2

function replace_text() {
// Get speadshhet with ID
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheets()[0];
// Returns cell with ID (User will insert his or her folder ID in cell B3)
var range = sheet.getRange(3, 2);
var values = range.getDisplayValue();
// Get folder by ID - insert your folder ID
var SourceFolder = DriveApp.getFolderById(values);
// Iterate throw all files in folder
var Files = SourceFolder.getFiles();
while(Files.hasNext()) {
var file = Files.next();
// Get all documents ID
var doc = DocumentApp.openById(file.getId());
// Get text body to replace
var body = doc.getBody();
// Insert header in document + alignment
var header = body.insertParagraph(0, 'TEXT');
header.setAlignment(DocumentApp.HorizontalAlignment.RIGHT)
// Text style
var style = {};
//style[DocumentApp.Attribute.HORIZONTAL_ALIGNMENT] = DocumentApp.HorizontalAlignment.RIGHT;
style[DocumentApp.Attribute.FONT_FAMILY] = 'Arial';
style[DocumentApp.Attribute.FONT_SIZE] = 9;
style[DocumentApp.Attribute.FOREGROUND_COLOR] = '#000000';
body.setAttributes(style)
Logger.log(body)
// Replacing text
body.replaceText("Text", " ");
body.replaceText("Date:\\s*\\d{2}\\.\\d{2}\\.\\d{4}", "31.10.2020")
var paragraphs = body.getParagraphs();
for (var i = 7; i < paragraphs.length; i++) {
var paragraph = paragraphs[i];
paragraph.setAlignment(DocumentApp.Horizontal`enter code here`Alignment.LEFT)
}
}
}