The Modern Programmer

Learn how to apply test coverage to your Typescripts projects.

Some naming conventions promote the use of the underscore character (" _ ") for those variables that must be declared but are not being used. One common case is that in which a function signature contains some variables that will not be used, as for instance the Express error handlers: app.use(function(err, req, res, next) { console.error(err.stack); res.status(500).send('Something broke!'); }); In the above example only the arguments err and res are being used, though all four must be defined in the handler signature. Thus, following the naming convention of using underscores for those unused variables, we could recode it as: app.use(function(err, _, res, __) { console.error(err.stack); res.status(500).send('Something broke!'); }); Though it makes the function more readable, it comes with a problem if using ESlint: it will blame by declaring unused variables. error '_' is defined but never used error '__' is define...

Linting and formatting tools are common in the Javascript/Typescript (JS/TS) scene, and their benefits are out of discussion: linters allows applying a set of coding style rules, whereas formatters apply a set of not coding but format style rules. Used in a development team scenario, its usage allows unifying the codebase by applying a common set of coding and formatting rules, no matter who the coder was. However, if not properly configured, these tools can collide in their functions, being the most common case the linter formatting code, a task that might be performed by the formatter. This article exposes the way of proceeding in order to allow both tools living in armony. Install and configure a linter The most common linter in the JS/TS scene is ESLint since TSLint , in the moment of writing this article, has been deprecated in favour of the first one. To install ESLint run these commands: $ npm install eslint --save-dev $ npx eslint --init Once installed you c...

How frustrating can be managing a big Typescript project in which all the module paths are relative to the importing file, as the next example. Every time we move a file, and therefore its relative path changes regarding its imported modules, we must sacrifice time and patience fixing a train of dots and slashes that too many times are fixed by trial and error. import {Request} from "express"; import {foo} from "../../../../types"; import {bar, baz} from "../../../../../myModules/bax"; Hopefully Typescript's tsconfig.json file allows specifying path aliases by setting the paths option. This option, together with the use of the npm package module-alias allows converting the previous mess into a piece of fine art: import {Request} from "express"; import {foo} from "@types"; import {bar, baz} from "@myModules/bax"; As said the process implies not just configuring tsconfig.json but also using the package...