Help me with Script to get text of indesign links

Thanks @eusoujpg, those demo files are helpful. You didn't include the expected output, so I will go by your instructions as best I can. Here is a script that collects the info and shows it, in CSV format, in an alert box. You can past in Excel, or change script to save to text file, etc.

- Mark

/**
 * @file Show Activities Info.js
 *
 * Displays linked indesign document information
 * including page number, link name, and content
 * of first 'activities' paragraph-styled paragraph
 * on the linked page.
 *
 * @author m1b
 * @discussion https://community.adobe.com/t5/indesign-discussions/help-me-with-script-to-get-text-of-indesign-links/m-p/14750067
 */
function main() {

    var doc = app.activeDocument,
        links = doc.links;

    var indds = [];

    // step 1: gather the indd links

    for (var i = 0; i < links.length; i++) {

        if (
            links[0].parent.itemLink
            && 'InDesign Format Name' === links[i].parent.itemLink.linkType
        )
            indds.push({ link: links[i], index: i, page: links[i].parent.parentPage });

    }

    // sort by Page index
    indds.sort(function (a, b) { return a.page.documentOffset - b.page.documentOffset });

    // step 2: gather the text of the activity

    app.findGrepPreferences = NothingEnum.NOTHING;

    for (var i = 0, indd, f, d, p, found; i < indds.length; i++) {

        indd = indds[i];
        indd.contents = '-- activity not found --';

        f = File(indd.link.filePath);

        if (!f.exists)
            continue;

        d = app.open(f, false);

        app.findGrepPreferences.appliedParagraphStyle = 'activity';

        p = d.pages.itemByName(String(indd.link.parent.pageNumber));

        if (!p.isValid)
            continue;

        found = d.findGrep();

        for (var j = 0; j < found.length; j++)
            if (found[j].parentTextFrames[0].parentPage === p)
                indd.contents = found[j].contents.replace(/[\n\r]/g, ' ');

        d.close(SaveOptions.NO);
        d = null;

    }

    // step 3: output

    var output = ['Page,Filename,Contents'];

    for (var i = 0, indd; i < indds.length; i++) {

        indd = indds[i];

        output.push(indd.page.name + ',' + indd.link.name + ',' + indd.contents);

    }

    alerter('Activities', output.join('\n'), 1000, 500);

};
app.doScript(main, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT, 'Show Activities');


/**
 * Show text in a multiline edit text field.
 * @param {String} title - the title of the alerter
 * @param {String|Array} obj - the text content (array of strings will work)
 * @param {Number} [width] - the dialog width
 * @param {Number} [height] - the dialog height
 */
function alerter(title, obj, width, height) {

    width = width || -1;
    height = height || -1;

    if (obj instanceof Array)
        obj = obj.join("\r");

    var w = new Window("dialog", title),
        et = w.add("edittext", undefined, obj, { multiline: true, scrolling: true }),
        closeButton = w.add("button", undefined, "Close", { name: "ok", alignment: ['right', 'center'] });

    et.maximumSize.height = w.maximumSize.height - 100;
    et.minimumSize.height = 350;
    et.minimumSize.width = 350;
    et.preferredSize = [width, height];

    w.show();

};

By the way, here is the output using your demo documents:

Page,Filename,Contents
1,ACTIVITS_2.indd,activity 1 “xxxx”
2,ACTIVITS_1.indd,activity 1 “xxxx”
3,ACTIVITS_2.indd,activity 2 “xxxx”
4,ACTIVITS_1.indd,activity 2 “xxxx”
5,ACTIVITS_3.indd,activity 1 “xxxx”
6,ACTIVITS_2.indd,activity 3 “xxxx”
7,ACTIVITS_3.indd,activity 2 “xxxx”
8,ACTIVITS_3.indd,activity 3 “xxxx”
9,ACTIVITS_1.indd,activity 3 “xxxx”