Indesign Script to alter page on data merge

Hi @dougw50331988, I do this all the time... like this example:

Goal: I want to do a data merge, but I want to assign a different master page depending on the "BRAND" field in the data csv file.

1) I make a field in the data file csv that corresponds to the master page name, if it doesn't already exist.

2) I make a text frame in the Indesign template document. I usually put it in the slug area, off the page, but slightly overlapping—the text frame must overlap the page or I think datamerge won't populate it. There are other ways to do this step but this is a simple approach. I assign a script label to this text frame, eg. "BRAND" so the script can read it later.

3) I do the data merge and now have a multi-page document, say 1000 pages. At the top of each page is the BRAND text frame (with the brand name or ID in it from the data csv file).

4) I run a script that assigns whatever master page matches the name in the BRAND text frame.

See script example below. I use this to (a) set the master page to match the brand, and (b) swap certain paragraph styles to match the brand. This isn't specific to your needs, but should help you understand.

- Mark

/**
 * Set Paragraph Styles and Master Pages.js
 * @author m1b
 * @version 2024-03-15
 *
 * Script to run after a datamerge
 * to apply master pages and paragraph styles
 * based on a "BASE BRAND" variable on each page.
 *
 * - the BASE BRAND variable is found in a text frame on each page.
 * - for each page, apply a master page named for that page's BASE BRAND.
 * - every paragraph of each page is checked, and if a paragraph style
 *   name matches the `brandMatcher` RegExp, then change the paragraph
 *   style to the style matching the page's BASE BRAND.
 *
 * If a master page or a paragraph style named for the BASE BRAND doesn't
 * exist, then the change won't be made. This can be intentional.
 */
function main() {

    var settings = {
        brandFrameName: 'BASE BRAND',
        brandMatcher: /^[^-]+/, // matches the prefix before a hyphen, eg. "myBrand-Body"
    };

    var doc = app.activeDocument,
        counter = 0;

    for (var i = 0, page, paras, len = doc.pages.length; i < len; i++) {

        page = doc.pages[i];
        paras = page.textFrames.everyItem().paragraphs.everyItem().getElements();

        var brandFrame = page.textFrames.itemByName(settings.brandFrameName);
        if (!brandFrame.isValid)
            continue;

        var newMaster = getThing(doc.masterSpreads, 'baseName', brandFrame.contents);

        if (newMaster && page.appliedMaster !== newMaster)
            page.appliedMaster = getThing(doc.masterSpreads, 'baseName', brandFrame.contents);

        doSomethingToThings(paras,
            function changeParagraphStyle(paragraph) {

                if (!paragraph.isValid)
                    return;

                var style = paragraph.appliedParagraphStyle,
                    match = style.name && style.name.match(settings.brandMatcher);

                if (!match)
                    return;

                var newStyle = getThing(doc.allParagraphStyles, 'name', style.name.replace(settings.brandMatcher, brandFrame.contents));

                if (!newStyle || newStyle === style)
                    return;

                paragraph.appliedParagraphStyle = newStyle;

                counter++;

            }
        );

    }

    alert(counter);

};

app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Set Paragraph Styles');

/**
 * Performs function `doThisTo` on each element of `things`.
 * @param {Array<*>} things - array of things.
 * @param {Function} doThisTo - the function to execute, given a thing.
 */
function doSomethingToThings(things, doThisTo) {

    for (var i = things.length - 1; i >= 0; i--)
        doThisTo(things[i]);

};

/**
 * Returns a thing with matching property.
 * @param {Array|collection} things - the things to look through, eg. PageItems.
 * @param {String} key - the property name, eg. 'name'.
 * @param {*} value - the value to match.
 * @returns {*} - the thing.
 */
function getThing(things, key, value) {

    for (var i = 0; i < things.length; i++)
        if (things[i][key] == value)
            return things[i];

};