Five pro tips for your next TypeScript code

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Shalitha Suranga

Sep 5 · 3 min read

I have been writing TypeScript code for around 2 years now. I thought to share some special things I used in codes I wrote.

JavaScript vs TypeScript

JavaScript started its journey a few decades back by doing simple dynamic things on web pages. But now JavaScript has very useful features such as classes support and powerful standard built-in objects like any other modern programming language. JavaScript is a dynamically typed programming language because the whole concept is to execute a source script in the user’s sandboxed environment via an interpreted way.

TypeScript is very popular because it introduced a new way that will help developers to write JavaScript using the statically typed concept. So it’s easy to identify data types before the execution of the code.

Let’s jump into the tips and tricks section!

Intersection and Union

There are situations where we need to pass different types of variables with the same parameter of a function and also where we need to combine properties of multiple variable types.

Union: Helpful when a specific function parameter supports multiple variable types.

Intersection: Merges two variable types into a single type which will have all the properties of given variable types.

Magic OR

If there are several variables and there is a need to set the truthy value to another variable, it could be simply solved using a couple of if conditions. But how about using instead for more cleaner and wise code?

Abstract properties

We all are familiar with abstract classes because we often use that concept to achieve well maintainable code using object oriented design principles. TypeScript supports abstract properties as well therefore we are able to define some abstract properties in a non-concrete class and use it via assigning some value in a concrete class.

External library definitions

Some TypeScript projects may use non-typescript global libraries. Our old friend Jquery is a good example. If the particular external library has TypeScript definitions there will be no issues with transpilation. Whereas if the particular external library is a custom one or not openly available one you can get away from transpilation errors using following tips.

The lazy way

Nothing but declaring the whole external library as any. For an example declaring of Jquery as

The active way

More correct way is to create your own TypeScript definitions for the external library (if it’s not publicly available). Simply create with the required definitions using interfaces or namespaces. For a simple example Typescript definitions of Neutralinojs can be found here

Your simple if condition could be wrong

Developers mostly use and to check whether a particular variable is available to use it or not. Importantly is not a truthy value in Javascript. Therefore, we need to be careful with truthy number checks.

In the above example, condition is not behaving correctly because could be too. Therefore if we modify the condition right to be on the point like everything will start behaving correctly as we expected.

Happy coding everyone!😎

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