1. Generate Key Number Javascript Map Array Example
2. Generate Key Number Javascript Map Array Example
3. Javascript Generate Array Of Numbers

Is there a way to generate sequence of characters or numbers in javascript? For example, I want to create array that contains eight 1s. I can do it with for loop, but wondering whether there is a. How to generate random number in given range using JavaScript? A number generated by a process, whose outcome is unpredictable is called Random Number. In JavaScript, this can be achieved by using Math.random function. Now I want a JSON format for Map Map in which Key should be Day and Value should be the Map having Key as Hours and Values as list of Hours which has same day. Something like this format.

Let’s step away from the individual data structures and talk about the iterations over them.

In the previous chapter we saw methods map.keys(), map.values(), map.entries().

These methods are generic, there is a common agreement to use them for data structures. If we ever create a data structure of our own, we should implement them too.

They are supported for:

• Map
• Set
• Array

Plain objects also support similar methods, but the syntax is a bit different.

Object.keys, values, entries

For plain objects, the following methods are available:

• Object.keys(obj) – returns an array of keys.
• Object.values(obj) – returns an array of values.
• Object.entries(obj) – returns an array of [key, value] pairs.

Please note the distinctions (compared to map for example):

The first difference is that we have to call Object.keys(obj), and not obj.keys().

Why so? The main reason is flexibility. Remember, objects are a base of all complex structures in JavaScript. So we may have an object of our own like data that implements its own data.values() method. And we still can call Object.values(data) on it.

The second difference is that Object.* methods return “real” array objects, not just an iterable. That’s mainly for historical reasons.

For instance:

• Object.keys(user) = ['name', 'age']
• Object.values(user) = ['John', 30]
• Object.entries(user) = [ ['name','John'], ['age',30] ]

Here’s an example of using Object.values to loop over property values:

Just like a for.in loop, these methods ignore properties that use Symbol(..) as keys.

Usually that’s convenient. But if we want symbolic keys too, then there’s a separate method Object.getOwnPropertySymbols that returns an array of only symbolic keys. Also, there exist a method Reflect.ownKeys(obj) that returns all keys.

Transforming objects

Objects lack many methods that exist for arrays, e.g. map, filter and others.

If we’d like to apply them, then we can use Object.entries followed Object.fromEntries:

1. Use Object.entries(obj) to get an array of key/value pairs from obj.
2. Use array methods on that array, e.g. map.
3. Use Object.fromEntries(array) on the resulting array to turn it back into an object.

For example, we have an object with prices, and would like to double them:

It may look difficult from the first sight, but becomes easy to understand after you use it once or twice. We can make powerful chains of transforms this way.

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.

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. ☝️

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 ?

Use the instructions in this section to create your own shell commands to generate your Apache CSR with OpenSSL. Private-Key File: Used to generate the CSR and later to secure and verify connections using the certificate. SSLCertificateChainFile is the DigiCert intermediate certificate file (e.g., DigiCertCA.crt). See Example: SSL Certificate - Generate a Key and CSR. Tableau Server uses Apache, which includes OpenSSL. You can use the OpenSSL toolkit to generate a key file and Certificate Signing Request (CSR) which can then be used to obtain a signed SSL certificate. The public key will be signed by a Certification Authority, and the result is a digital certificate (which can be in a CRT file) My point is: if you have a CRT file (aka certificate), it means a key pair was already generated and signed by a Certification Authority. There's no way to generate a new key from it (because it already has a key). Generate key and crt file apache openssl. Jul 08, 2009  You can also generate self signed SSL certificate for testing purpose. In this article, let us review how to generate private key file (server.key), certificate signing request file (server.csr) and webserver certificate file (server.crt) that can be used on Apache server with modssl. Key, CSR and CRT File Naming Convention. Apache - Generate private key from an existing.crt file. Ask Question. Because the.key file is the one I made myself. Is there any way to generate the proper.key file from the.crt? Apache-httpd ssl. I've dealt with.p12 files where I've needed to extract the.key file from it. $ openssl pkcs12 -in starqmetricstechcom.p12 -out star.

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 ?

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:

Generate Key Number Javascript Map Array Example

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.

However, it is recommended that you specify a passphrase to protect your private key against unauthorized use. Generate public private key pair unix software. Otherwise, enter the required path and file name, and then press Enter.The command prompts you to enter a passphrase.The passphrase is not mandatory if you want to log in to an instance created using an Oracle-provided image. To accept the default path and file name, press Enter. For example: /home/ username/.ssh/idrsa.

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! ⬇⬇ ??

Generate Key Number Javascript Map Array Example

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…

Javascript Generate Array Of Numbers

Thanks for reading ❤️