Question about array and html

Why in this code

var x = [4, 9, 16, 25];
document.getElementById("demo").innerHTML = x;

Does the inner HTML show the numbers without the square brackets? (AKA how come it does not insert the array?)

And in this code

class BusinessList extends React.Component {
    render() {
        return (
            <div className="BusinessList">
                {
                this.props.businesses.map(business => {
                    return <Business business={business} />
                })
                }
            </div>
        )
    }
}

I have the same question + does the div look like this:

<div>
    <Business business={business} />, <Business business={business} />, etc.
</div>

If so isn’t this the incorrect format?

Thanks!