The curly braces only need to be used within JSX elements. Like this:
<MyComponent somProp={['something']} />
In the case above, the {} is the way of saying: “Evaluate the expression that I passed within and pass it as a prop”. Within the {} you can pass any valid JavaScript object or expression. Note that if you pass a string, and specifically for strings, you don’t need the curly braces… like <MyComponent somProp="something" />.
The above code is the equivalent of this:
var myArray = ['something'];
<MyComponent somProp={myArray} />