all_indexes.js

db = db.getSiblingDB("admin");
dbs = db.runCommand({ "listDatabases": 1 }).databases;
dbs.forEach(function(database) {
    db = db.getSiblingDB(database.name);
    cols = db.getCollectionNames();
    cols.forEach(function(col) {
        print(`*** ${col} ***`);
        printjson(db.getCollection(col).getIndexes());
    });
});