1. Q&A for Work. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.
2. Mar 13, 2017 This means we can target values in an array and change them, unlike strings. Modify Array Data With Indexes, freeCodeCamp Basic Javascript We Will Code. How to create Data Entry Form in.

1. Freecodecamp Generate An Array With Object.keys Keyboard
2. Freecodecamp Generate An Array With Object.keys In Javascript
3. Freecodecamp Generate An Array With Object.keys Letters

Generate an Array of All Object Keys with Object.keys; Generate an Array of All Object Keys with Object.keys Method: To return the array of users the Object.keys method must take an arguement. This challenge can be solved using a single line return statement. Jun 25, 2018 In order to get keys of any object the syntax is Object.keys(objectname). This returns an array. In this challenge we have a nested Object,meaning we have keys which also contains objects and we need to list them all. Here is the function that I wrote to get all the keys: function getArrayOfUsers(obj). Learn to code at home. Build projects. Earn certifications. Since 2014, more than 40,000 freeCodeCamp.org graduates have gotten jobs at tech companies including Google, Apple, Amazon,. Learn to code. Build projects. Earn certifications.Since 2015, 40,000 graduates have gotten jobs at tech companies including Google, Apple, Amazon, and Microsoft.

Join GitHub today

GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Comments

by Alex Permyakov

When you read about Array.reduce and how cool it is, the first and sometimes the only example you find is the sum of numbers. This is not our definition of ‘useful’. ?

Moreover, I’ve never seen it in a real codebase. But, what I’ve seen a lot is 7–8 line for-loop statements for solving a regular task where Array.reduce could do it in one line.

Recently I rewrote a few modules using these great functions. It surprised me how simplified the codebase became. So, below is a list of goodies.

If you have a good example of using a map or reduce method — post it in the comments section. ?

Let’s get started!

1. Remove duplicates from an array of numbers/strings

Well, this is the only one not about map/reduce/filter, but it’s so compact that it was hard not to put it in the list. Plus we’ll use it in a few examples too.

2. A simple search (case-sensitive)

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

3. A simple search (case-insensitive)

4. Check if any of the users have admin rights

The some() method tests whether at least one element in the array passes the test implemented by the provided function.

5. Flattening an array of arrays

The result of the first iteration is equal to : […[], …[1, 2, 3]] means it transforms to [1, 2, 3] — this value we provide as an ‘acc’ on the second iteration and so on.

Microsoft office 2013 activation key generator windows 8. Jan 26, 2020  The Microsoft Office 2013 Product Key Generator is a free tool that is used to generate the activation keys for Microsoft Office 2013 for life. It must be the activation process after installing Microsoft Office 2013, but don’t worry, there is a tremendous tool that is used for the activation of Microsoft Products.

We can slightly improve this code by omitting an empty array[]as the second argument for reduce(). Then the first value of the nested will be used as the initial acc value. Thanks to Vladimir Efanov.

Note that using the spread operator inside a reduce is not great for performance. This example is a case when measuring performance makes sense for your use-case. ☝️

Freecodecamp Generate An Array With Object.keys Keyboard

Thanks to Paweł Wolak, here is a shorter way without Array.reduce:

Also Array.flat is coming, but it’s still an experimental feature.

6. Create an object that contains the frequency of the specified key

Let’s group and count the ‘age’ property for each item in the array:

Thanks to sai krishna for suggesting this one!

7. Indexing an array of objects (lookup table)

Instead of processing the whole array for finding a user by id, we can construct an object where the user’s id represents a key (with constant searching time).

It’s useful when you have to access your data by id like uTable[85].name a lot.

8. Extract the unique values for the given key of each item in the array

Let’s create a list of existing users’ groups. The map() method creates a new array with the results of calling a provided function on every element in the calling array.

9. Object key-value map reversal

This one-liner looks quite tricky. We use the comma operator here, and it means we return the last value in parenthesis — acc. Let’s rewrite this example in a more production-ready and performant way:

Here we don’t use spread operator — it creates a new array on each reduce() call, which leads to a big performance penalty: O(n²). Instead the old good push() method.

10. Create an array of Fahrenheit values from an array of Celsius values

Think of it as processing each element with a given formula ?

11. Encode an object into a query string

12. Print a table of users as a readable string only with specified keys

Sometimes you want to print your array of objects with selected keys as a string, but you realize that JSON.stringify is not that great ?

Freecodecamp Generate An Array With Object.keys In Javascript

JSON.stringify can make the string output more readable, but not as a table:

13. Find and replace a key-value pair in an array of objects

Let’s say we want to change John’s age. If you know the index, you can write this line: users[1].age = 29. However, let’s take a look at another way of doing it:

Here instead of changing the single item in our array, we create a new one with only one element different. Now we can compare our arrays just by reference like updatedUsers users which is super quick! React.js uses this approach to speed up the reconciliation process. Here is an explanation.

14. Union (A ∪ B) of arrays

Less code than importing and calling the lodash method union.

15. Intersection (A ∩ B) of arrays

The last one!

As an exercise try to implement difference (A B) of the arrays. Hint: use an exclamation mark.

Thanks to Asmor and incarnatethegreat for their comments about #9.

That’s it!

If you have any questions or feedback, let me know in the comments down below or ping me on Twitter.

If this was useful, please click the clap ? button down below a few times to show your support! ⬇⬇ ??

Here are more articles I’ve written:

Production ready Node.js REST APIs Setup using TypeScript, PostgreSQL and Redis.
A month ago I was given a task to build a simple Search API. All It had to do is to grab some data from 3rd party…

Freecodecamp Generate An Array With Object.keys Letters

Thanks for reading ❤️