To store data we can use either object or we can use array in javascript. Both have their own advantage and disadvantage. Array : Array has advantage of maintaining order, but negative side is that If you want to update any element inside array you have to find the index of the element. May be via looping through the whole array if indexes are not predictable. Object : You can store element as object property. It's like key-value pair, So If you want to update any property (element) of object, you can update it easily using key. So, It's easy to update the elements in object, but object uses hash for property, So order is not guaranteed. Immutable.js with firebase Firebase provides live updates. Suppose you are having a program where you are listening for live updates on some last x elements, while retaining others for display only, but order of display matters. You are listening for last x elements live, So you have to update the data of those elements when you receive upd...