To create an array of persons:

var persons = []; // initialize the array

persons.push({firstName:"John", lastName:"Doe", age:46}); // Add an object

persons.push({firstName:"Joanne", lastName:"Doe", age:43}); // Add another object

To retrieve the value at a specific index:

persons[1].firstName // "Joanne"
persons[1].lastName  // "Doe"
persons[1].age       // 43

To iterate through the array use a for loop, or any kind of loop:

for (var i = 0; i < persons.length; i++) {
    console.log( persons[i].firstName ); // writes first names to console
}

Creating an array is as simple as this:

var cups = [];

You can create a populated array like this:

var cups = [
    {
        color:'Blue'
    },
    {
        color:'Green'
    }
];

You can add more items to the array like this:

cups.push({
    color:"Red"
});

MDN array documentation

Kill the braces.

var defaults = {
 backgroundcolor: '#000',
 color: '#fff',
 weekdays: ['sun','mon','tue','wed','thu','fri','sat']
};

var list = [
    { date: '12/1/2011', reading: 3, id: 20055 },
    { date: '13/1/2011', reading: 5, id: 20053 },
    { date: '14/1/2011', reading: 6, id: 45652 }
];

and then access it:

alert(list[1].date);

Here is a shorter way of achieving it:

let result = objArray.map(a => a.foo);

OR

let result = objArray.map(({ foo }) => foo)

You can also check Array.prototype.map().