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Hands-on JavaScript for Python Developers

You're reading from   Hands-on JavaScript for Python Developers Leverage your Python knowledge to quickly learn JavaScript and advance your web development career

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Product type Paperback
Published in Sep 2020
Publisher Packt
ISBN-13 9781838648121
Length 410 pages
Edition 1st Edition
Languages
Tools
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Author (1):
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 Nagale Nagale
Author Profile Icon Nagale
Nagale
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Toc

Table of Contents (26) Chapters Close

Preface 1. Section 1 - What is JavaScript? What is it not?
2. The Entrance of JavaScript into Mainstream Programming FREE CHAPTER 3. Can We Use JavaScript Server-Side? Sure! 4. Nitty-Gritty Grammar 5. Data and Your Friend, JSON 6. Section 2 - Using JavaScript on the Front-End
7. Hello World! and Beyond: Your First Application 8. The Document Object Model (DOM) 9. Events, Event-Driven Design, and APIs 10. Working with Frameworks and Libraries 11. Deciphering Error Messages and Performance Leaks 12. JavaScript, Ruler of the Frontend 13. Section 3 - The Back-End: Node.js vs. Python
14. What Is Node.js? 15. Node.js versus Python 16. Using Express 17. React with Django 18. Combining Node.js with the Frontend 19. Enter Webpack 20. Section 4 - Communicating with Databases
21. Security and Keys 22. Node.js and MongoDB 23. Putting It All Together 24. Assessments 25. Other Books You May Enjoy

Step 2 – retrieval

Now, let's write our retrieval function:

const getProducts = function(a,b) {
// make an efficient means of retrieval
if (products[a]) {
return products[a][b] || null
}
return null
}

If we look at this logic, first we ensure the first key exists. If it exists, we return either x.y or null if y does not exist. Objects are picky in that if you try to refer to a value of a key that doesn't exist, you'll get an error. Thus, we first need to existence-check our key. If the key exists and the key/value pair exists, return the computed value; otherwise, we return null. Notice the return products[a][b] || null short-circuit: this is an efficient way of saying "return the value or something else." If products[a][b] does not exist, it will respond with a falsy value, and the OR operation will take over. Efficient!

Take a look at the solution code for the answer to the bonus question. The same principles of existence...

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