Hands-On JavaScript High Performance

Writing safe mutable code

Before we move on to writing safe mutable code, we need to discuss references and values. A value can be considered anything that is a primitive type. Primitive types, in JavaScript, are anything that are not considered objects. To put it simply, numbers, strings, Booleans, null, and undefined are values. This means that if you create a new variable and assign it to the original, it will actually give it a new value. What does this mean for our code then? Well, we saw earlier with Redux that it was not able to see that we updated a property in our state system, so our previous state and current state showed they were the same. This is due to a shallow equality test. This basic test tests whether the two variables ...