Copying Google Doc Header Formatting with GAS - google-apps-script

Question

I'm trying to copy a Header/Footer from the active Doc acting as a template to a newly created Doc. I'm able to get the text easy enough, but I'm not able to get the formatting, fonts or horizontal alignment.
My theory was that I could do something like
newDocHeader.setAttributes(activeDocHeader.getAttributes());
But, I still only see plain text that is left aligned. When inspecting the attributes object on the header i get the following:
({
FONT_SIZE:null,
ITALIC:null,
STRIKETHROUGH:null,
FOREGROUND_COLOR:null,
BOLD:null,
LINK_URL:null,
UNDERLINE:null,
FONT_FAMILY:null,
BACKGROUND_COLOR:null
})
I tried to loop through the Child objects of the Header and perform a similar setAttributes(getAttributes) on each child, but to no avail.
I also thought the copy() function on the Header/Footer object would be promising, but when I tried
newDocFooter = activeDocFooter.copy();
But, this produces a blank footer with no text or formatting.
Is there a good way to copy the formatting, font and horizontal alignment from one Header/Footer to another?

Answer 1

I'm entirely unfamiliar with DocumentApp, but this broadly worked for me:
/**
* Copies headers from one document to another.
* #param {string} source The source document URL.
* #param {string} target The target document URL.
*/
function copyHeader(source, target) {
// Used to map from child types to required "append<X>" method
var functionMap = {
PARAGRAPH: 'appendParagraph',
LIST_ITEM: 'appendListItem',
HORIZONTAL_RULE: 'appendHorizontalRule',
IMAGE: 'appendImage',
TABLE: 'appendTable'
};
var t = DocumentApp.openByUrl(target);
var s = DocumentApp.openByUrl(source);
var sourceHeader = s.getHeader();
var targetHeader = t.getHeader();
// If there is no header in the target doc, add one
if (!targetHeader) {
targetHeader = t.addHeader();
}
targetHeader.clear();
// Docs requires one child element, so one will remain even
// after clearing. Get a reference to it so it can be removed
var targetNumChild = targetHeader.getNumChildren();
if (targetNumChild === 1) {
var placeholderElement = targetHeader.getChild(0);
}
// Copy across each element to the target doc
var c = sourceHeader.getNumChildren();
for (var i = 0; i < c; i++) {
var element = sourceHeader.getChild(i).copy();
var method = functionMap[element.getType()];
targetHeader[method](element);
}
// Remove the saved element if required
if (targetHeader.getNumChildren() > 1 && placeholderElement) {
targetHeader.removeChild(placeholderElement);
}
}
I say broadly only because formatting such as bold, horizontal centering, horizontal rules etc all copied across fine, but bizarrely, lists seem to change from being numbered to being bulleted, so something was lost in translation.
It might need a little tweaking, and surely there is an easier way, but in the absence of anything else, this might be a start.
Source document:
Target document, note that the list type isn't quite right!:
Hope it helps.