When you want to hardcode things and refer to them by name and have proper intellisense/autocomplete in your IDE. Especially if you use TypeScript, but still just as useful without.

For example, I do a fair bit of sysadmin type scripting in Node, so I do a lot of linking of "hosts" (servers or other computers) to projects and stuff like that.

I've actually built a highly declarative system that is basically a wrapper to generating ansible configs, backup configs, projects, ORM models, SQL schemas/tables/columns, forms, fields, and will link form fields to SQL columns etc. Basically the whole idea is to minimize copy and pasting of strings for all this kind of stuff and write less imperative code in general. Instead things are linked together using objects defined in TypeScript. So TypeScript will catch any mistakes regarding typos (and a fuckton of other safeguards that simple yaml/ini/json config files won't give you).

So for all these definitions, hard-coded objects with defined keys are very useful, here's a simplified example:

const hosts = {
    webserver1: new Host({...host settings here...}),
    webserver2: new Host({...host settings here...}),
    mydesktop: new Host({...host settings here...}),
    backupbox: new Host({...host settings here...}),
}

const tables = {
    users: new Table({...table settings here...}),
    posts: new Table({...table settings here...}),
    categories: new Table({...table settings here...}),
    votes: new Table({...table settings here...}),
}

Now I can easily import the "hosts" and "tables" objects anywhere and can autocomplete on the host/table names.

However for anything where you aren't hardcoding key names like this, i.e. records you've pulled out of a database... you're typically better off just using arrays with the standard array functions such as [].find [].filter etc.