getElementById() wildcard

Try this in 2019 as a wildcard.

document.querySelectorAll("[id*=path_test_]")

Not in native JavaScript. You have various options:

1) Put a class and use getElementsByClassName but it doesn't work in every browser.

2) Make your own function. Something like:

function getElementsStartsWithId( id ) {
  var children = document.body.getElementsByTagName('*');
  var elements = [], child;
  for (var i = 0, length = children.length; i < length; i++) {
    child = children[i];
    if (child.id.substr(0, id.length) == id)
      elements.push(child);
  }
  return elements;
}

3) Use a library or a CSS selector. Like jQuery ;)

In one of the comments you say:

(...) IE is anyway banned on my page, because he doesn't get it with CSS. It's an admin tool for developer, so only a few people, and they will anyway use FF

I think you should follow a different approach from the beginning, but for what it's worth, in the newer browsers (ok, FF3.5), you can use document.querySelectorAll() with which you can get similar results like jQuery:

var elements = document.querySelectorAll('[id^=foo]');
// selects elements which IDs start with foo

Update: querySelectorAll() is only not supported in IE < 8 and FF 3.0.

jQuery allows you to find elements where a particular attribute starts with a specific value

In jQuery you would use

$('[id^="path_test_"]')