Well, let's see

    var mostRecent = '';

    if (type(c.messages) === 'array' ||
        type(c.messages[0]) === 'object' ||
        type(c.messages[0].text) === 'string') {
        mostRecent = c.messages[0].text.substring(0, 30);
    }

    return name + ': ' + mostRecent;

.. apart from the fact that he probably meant && instead of || in that condition, we've also now got a system that silently swallows errors. Bugs can lurk in it without any more symptoms than producing empty strings where more interesting strings were expected.

I much prefer my systems to crash when a programmer made an error, and do so noisily and detectably, so that the problem can be fixed. I also prefer the actual logic of my code to make up more than 20% of the lines. If you're going to add boilerplate type checks all over, the signal-to-noise ratio gets really bad.

So don't do this. Use Typescript if you want to check types.