So using reduce, we’ll create the basic structure. In fact, most times you think you need to do array method chaining, you can replace them with reduce. So since they are both reduction operations, we can replace both of them with a single reduce. Based off of our deep dive into both methods, what do we know about both of them? That they can both be implemented with reduce. However, let be give you a quick tip for doing a map and filter transformation. So one approach would be to chain on map and then filter. You might be saying that we need to use two methods, map and filter, because we want to both transform and filter the array. So based of these two criteria, think for a second and take a guess about what array method we need to use… So let’s think about what we want to do: we need to transform the data into an array of object, which we also want to filter based on a condition. Now we can chain on any array method we need to get the job done. Replacing map / filter with a single reduce And since we have an implicit return with our arrow function, the accumulator will always be returned:įor each nested array, we have the key, or the id of the user as the first element and the value, or the user object as the second element. The shorthand to do this operation is to say acc + expense. Then we have our accumulator, and each element will be an expense. First our return value will be as a number, so our initial value will be 0. And then using the reduce method, we can sum everything in one line. How would you combine Object.values and reduce to get a monthly total of all John’s expenses…įirst we could create a variable, monthlyTotal, get the array of values, the cost of each expense.
And we know how to easily get the sum of an array of numbers using reduce. We could come up with some way of doing this using a for in loop or something, but it’s not nearly as easy as throwing all of the values in a single array. How would we easily get a sum total of all of these combined expenses?
Try to imagine if this had even more properties than it does. Enter fullscreen mode Exit fullscreen mode
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