#typescript

If I went back in time 5 years and told myself that I would eventually work toward a bachelor’s degree in math, I never would have believed it. All throughout high school and even my freshman year of college, I had the same thought in every math class I took: “When would I ever use this in real life?” It was not until my first course in differential equations that I realized how useful and applicable mathematics can be to solve real life problems. However, these problems mainly involved physics and finance, neither of which are of interest to me. I enjoyed all my computer science classes but with a BS in computer science I was not going to graduate on time after transferring my freshman year. Choosing a concentration in computing allowed me to take a class on scientific computing — a class teaching you how to utilize computer science to write efficient programs that solve complicated systems of linear equations as well as estimate differential equations that cannot be solved exactly by any known methods.

A system of linear equations is a set of two or more multivariable equations, involving the same variables. For example: 2x + 2y = 4, 3x – y = 2, where x represents the same value in both equations as does y. A system of two linear equations, both involving only two variables can be solved simply by solving one for y, and plugging that y value into the other equation:

2x + 2y = 4 → 2y = 4 - 2x → y = (2 - x) …. 
3x - y = 2 → 3x - (2 - x) = 2 → 3x - 2 + x = 2 → 4x = 4 → x = 1 …. 
y = 2 - x → y = 2- (1) = 1 …. 

The solution is therefore x=1, y=1.

When you have many more equations as well as more variables than 2, solving by hand becomes less practical and can be virtually impossible in a system of 200 equations involve 200 variables.

To combat this, you can use represent the system of equations in a matrix, and solve through a process called Gaussian elimination. In Gaussian elimination, you can manipulate and reduce a matrix to a form where only the diagonal and everything above consist of numbers while everything below is 0. From there, the system is easy to solve. This can be simple for 3 x 3 matrices, but when you increase the dimensions it becomes impractical. The solution is to implement Gaussian elimination in a coding language. The course I took on scientific computing utilized MATLAB because MATLAB is built for numerical computations through matrices. As a challenge, I worked on implementing Gaussian elimination in Typescript. Using the math.js library to create and manipulate matrices as well as some help from Martin Thoma’s website at https://martin-thoma.com/solving-linear-equations-with-gaussian-elimination/, I was able to create a working program that can solve a system of equations of the form:

1x - 3y + 1z = 4
2x - 8y + 8z = -2
-6x + 3y -15z = 9

The above gives the exact solution x = 3, y = -1, and z = -2.

Implementing this in typescript was challenging at first, as matrix manipulation through the math.js library is much more complex than my experience in MATLAB. However, it was interesting to apply something I learned in a university course to a real world work situation. Since I am looking toward a career somewhere in the computer science field, a lot of the math courses I take are not fully relevant to what I will do later in life — though they really help when it comes to problem solving and thinking outside the box. Utilizing topics I have learned in class to make programs such as these makes the difficulty of majoring in mathematics well worth it!

Check out the code at https://github.com/Setfive/ts-base/blob/master/src/GaussElim.ts and a live demo below!

Posted In: General, TypeScript

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Note: This post originally appeared at Codeburst

At Setfive Consulting we’ve become big fans of using TypeScript on the frontend and have recently begun adopting it for backend nodejs projects as well. We’ve picked up a couple of tips while setting up these projects that we’re excited to share here!

Directory structure

For most nodejs projects any directory layout will work and what you pick will be a matter of personal preference. TypeScript is similar but in order to get the TypeScript compiler to generate JavaScript code into a “dist/” you’ll need to write your code inside a separate directory like “src/” within your project. So you’ll want a layout like the following:

And the compiler will produce JavaScript code in “dist/” from your TypeScript sources in “src/”.

Setup tsconfig.json

As you can see above you’ll want a tsconfig.json file to configure the behavior of the TypeScript compiler. tsconfig.json is a special JSON configuration file that automatically sets various flags for you when you run “tsc” with it present. You can see an exhaustive list of the available options at here. We’ve been using the following as a solid starting point:

From a build perspective this will configure a couple of things for you:

  • sourceMaps are enabled so you’ll be able to use node’s DevTools integration to view TypeScript sources alongside your JavaScript
  • The compiler will output into a “dist/” folder
  • And it’ll compile all of your source files under the “src/” directory

ts-node and nodemon

One of the stumbling blocks to using TypeScript with nodejs is the required compilation step. At face value, it seems like the required workflow would be to edit a TypeScript file, run the compiler, and then run the generated JavaScript on node. Thankfully, ts-node and nodemon make that a reality you wont have to suffer.

ts-node is basically a wrapper around your nodejs installation that will allow you to run TypeScript files directly, without invoking the compiler. Their Readme highlights how it works:

TypeScript Node works by registering the TypeScript compiler for the .ts, .tsx and – when allowJs is enabled – .js extensions. When node.js has a file extension registered (the require.extensions object), it will use the extension internally with module resolution. By default, when an extension is unknown to node.js, it will fallback to handling the file as .js (JavaScript).

So with ts-node you’ll be able to run something like “ts-node src/index.ts” to run your code.

nodemon is the second piece of the puzzle. It’s a node utility that will monitor your source files for changes and automatically restart a node process for your. Perfect for building express or any server apps! We’ve been using the following nodemon.json config file:

And then you’ll be able to just invoke “nodemon” from the root of your project.

Remember “@types/” packages

Since you’re writing nodejs code chances are you’re going to want to leverage JavaScript libraries. TypeScript can interoperate with JavaScript but in order for the compiler to compile without errors you’ll need to provide “.d.ts” typings for the libraries you’re using. For example, trying to compile the following:

import * as _ from "lodash";
console.log(_.range(0, 10).join(","));

Will result in a TypeScript error:

src/index.ts(1,20): error TS7016: Could not find a declaration file for module ‘lodash’. ‘/home/ashish/Downloads/node_modules/lodash/lodash.js’ implicitly has an ‘any’ type.
Try `npm install @types/lodash` if it exists or add a new declaration (.d.ts) file containing `declare module ‘lodash’;`

Even though the output JavaScript file was successfully generated.

The “.d.ts” files are type definitions for a JavaScript library describing the types used, function signatures, and any other type information the compiler might need.

Several popular JavaScript libraries, like moment, have begun shipping the typings files within their main project but many others, like lodash, haven’t. In order to get libraries that don’t have the “.d.ts” files within their main project to work you’ll have to install their respective “@types/” packages. The “@types/” namespace is maintained by DefinitelyTyped but the definitions themselves have been written by contributors. Installing “@types/” packages is easy:

npm install — save @types/lodash

And now the compiler will run without any errors.

Off to the races!

At this point you should have a solid foundation for a TypeScript powered nodejs project. You’ll be able to take advantage of TypeScript’s powerful type system, nodejs’ enormous library ecosystem, and enjoy a easy to use “save and reload” workflow. And as always, I’d love any feedback or other tips!

Thinking about adopting TypeScript at your organization? We’d love to chat.

Posted In: TypeScript

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We recently started a new project and decided to use TypeScript along with Angular 1.5. Angular 1.5 introduces a new abstraction called a “component” which closely resembles Angular 2’s component based approach. Surprisingly, there isn’t a lot of simple TypeScript sample code available for Angular 1.5 so I decided to throw something together in case anyone else is looking. The code is available at https://github.com/Setfive/ng_typescript_starter and a live demo of it is running at http://code.setfive.com/ng_typescript_starter.

So what are some standouts with TypeScript and Angular 1.5?

  • The 1 way bindings components introduce are easier to reason about but having to explicitly add functions for “outputs” does add some verbosity
  • Related to that, there’s a fair amount of boilerplate to create a single component since you have to define 2 classes
  • Dropping $scope in favor of automatically binding the controller object to $ctrl in templates is great – especially with TypeScript classes
  • Related to that, without $scope for events it’s unclear when it’s appropriate to use $rootScope for an event bus
  • You can write typesafe code for almost all of your controller business logic
  • It’s really unfortunate the TypeScript compiler can’t typecheck your Angular templates
  • Using the $inject annotation with component classes looks “right” versus the “array like” syntax
  • You need to be somewhat cognizant of matching your @types annotations with the correct version of the library you’re using
  • Using components with ui-router makes it fairly difficult to communicate between sibling views

Anyway, beyond fighting with build tools to convert a TypeScript project into usable JavaScript the language part has been great to work with. We ended up using Browserify with tsify but it was pretty frustrating to get it working. I might of missed something but it seems like I needed tsify available in a separate node_modules directory from the project source. The demo app is setup this way for that reason.

As always, questions and comments are welcome!

Posted In: AngularJS, Javascript

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Over the past few day we’ve been evaluating using Angular 1.x vs. Angular 2 for a new project on which in the past we would have used Angular 1.x without much debate. However, with release of Angular 2 around the corner we decided to evaluate what starting a project with Angular 2 would involve. As we started digging in it became clear that using Angular 2 without programming in TypeScript would be technically possible but painful to put it lightly. Because of the tight timeline of the project we decided that was too large of a technical risk so we decided to move forward with 1.x. But I decided to spend some time looking at TypeScript anyway, for science. I didn’t have anything substantial to write but needed to hammer out a quick HTML scraper so I decided to whip it up in TypeScript.

Getting started with TypeScript is easy you just use npm to install the tranpiler and you’re off to the races. As I started experimenting, I fired up PhpStorm 10+ and was thrilled to learn it has good TypeScript support out of the box (thanks JetBrains!). The scraper I was writing is pretty simple – make a series of HTTP requests, extract some elements out of the HTML via CSS selectors, and write the results out to a CSV. Coming from a JavaScript background, jumping right into TypeScript was easy enough since TypeScripts’ syntax is basically ES2015 with additional Java or C# like type declarations. The scraper is less than 100 lines so I didn’t get a great sense of what programming with TypeScript would be like but here are some initial takeaways.

It’s easy to end up missing out on the benefits. Since TypeScript is a superset of JavaScript you’re free to ignore all the type features and write TypeScript that is basically ES2015. Combine that with the fact that the tsc transpiler will produce JavaScript even with type errors and you can quickly find yourself not enjoying any of the benefits TypeScripts introduces. This issue isn’t unique to TypeScript since you can famously write You Can Write FORTRAN in any Language but I think since its a superset of an existing, popular langue the temptation is much stronger.

Discovering functionality in modules is easier. In order to properly interface with nodejs modules you’ll need to grab type definitions from somewhere like DefinitelyTyped. The definition files are similar to “.h” files from C++, code stubs that just provide function type signatures to TypeScript. An awesome benefit of this is that it’s much easier to “discover” the functionality of nodejs modules by looking at how the functions transform data between types. It also makes it much easier to figure out the parameters of a callback without having to dig into docs or code.

Typed generics will unequivocally reduce bugs. I’d bet a beer or two that most web developers spend the majority of their day writing code that deals with lists. Creating them, filtering them, transforming them, etc. Unfortunately, most of the popular scripting languages don’t have support for typed generics and specifically enforcing uniform types within arrays. Specifically with JavaScript, it’s pretty easy to end up at a point where you’re unsure of what’s contained in a list and moreover if the objects within it share any of the same properties. Because of this, I think TypeScript’s typed generics will cut down on bugs almost immediately.

TypeScript is definitely interesting and it’s tight coupling to Angular 2 only bolsters how useful it’ll be in the future. Next up, I’d be interested in building something more substantial with both a client and server component and hopefully share some of the same code on both.

As always, questions and comments are more than welcome!

Posted In: Javascript

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