Using Array Spread syntax and Object Destructing -- Return the first element of an array as a property of an object.

return-first-child-in-array.js

{
    let elementA = {
        name: 'xyz',
        children: [ 
            { name: 'abc' }, // firstChild
            { name: 'bcd'}   // secondChild
        ]
    };
    const getFirst = (d = []) => ([f, ...r] = d, f);
    const firstChild = getFirst(elementA.children);
    console.log(`I only want the first child: ${(firstChild === elementA.children[0] ? 'Yay! Got it.' : 'Nope.')}`);
}