I am trying to solve “A very big sum” challenge on Hacker Rank: https://www.hackerrank.com/challenges/a-very-big-sum/problem In there I have to sum all the numbers in the array given so I came up with two solutions: First solution Second Solution But none of them work and I don´t know why, I am th…
Tag: reduce
Using reduce() to find min and max values?
I have this code for a class where I’m supposed to use the reduce() method to find the min and max values in an array. However, we are required to use only a single call to reduce. The return array should be of size 2, but I know that the reduce() method always returns an array of size 1. I’m
JavaScript array .reduce with async/await
Seem to be having some issues incorporating async/await with .reduce(), like so: The data object is logged before the this.store completes… I know you can utilise Promise.all with async loops, but does that apply to .reduce()? Answer The problem is that your accumulator values are promises – they&…
JavaScript – examples of reduce() function
I’m looking at this example of use of reduce() function. Could you give show me some other examples of using reduce() – I’m not sure I fully follow how it works. Thank you Answer What reduces does is take an initialValue, a function with 2 essential parameters (can take more) and a list of v…
Javascript Object to querystring using reduce
I’m having trouble to apply a reduce to an Object to get it in a querystring format. I want this: So far, the close I have got is this: which gives me: Is there an easier way to achieve this without have to prepend the initialValue and remove the & later? EDIT: This question is old and today we can
reduce function composed of map function in JavaScript
Say we have and want to reduce() it like Now, I want to compose reduce() function itself from map() function. How would you do that? What is the smartest way? Edit: In the comments and answers, many have claimed fold/reduce can compose map, in shallow level, that can be true, however, in category theory, fund…
Sum JavaScript object propertyA values with the same object propertyB in an array of objects
How would one take a JavaScript array of objects, such as and merge duplicate keys by summing the values? In order to get something like this: I have tried iterating and adding to a new array, but this didn’t work: Answer You should be assigning each object not found to the result with its .key property…
Javascript reduce() on Object
There is nice Array method reduce() to get one value from the Array. Example: What is the best way to achieve the same with objects? I’d like to do this: However, Object does not seem to have any reduce() method implemented. Answer What you actually want in this case are the Object.values. Here is a con…