{"id":71636,"date":"2020-01-10T16:00:36","date_gmt":"2020-01-10T10:30:36","guid":{"rendered":"https:\/\/www.vskills.in\/certification\/tutorial\/?p=71636"},"modified":"2024-04-12T14:22:36","modified_gmt":"2024-04-12T08:52:36","slug":"typescript-basics-2","status":"publish","type":"page","link":"https:\/\/www.vskills.in\/certification\/tutorial\/typescript-basics-2\/","title":{"rendered":"TypeScript Basics"},"content":{"rendered":"\n

Go back to Tutorial<\/a><\/p>\n\n\n

Install the TypeScript transpiler using npm:<\/p>\n

$ npm install -g typescript<\/p>\n

Then use tsc to manually compile a TypeScript source file into ES5:<\/p>\n

$ tsc test.ts<\/p>\n

$ node test.js<\/p>\n

TypeScript is more demanding than ES6 and it expects instance properties to be declared:<\/p>\n

class Pizza {<\/p>\n

toppings: string[];<\/p>\n

constructor(toppings: string[]) {<\/p>\n

this.toppings = toppings;<\/p>\n

}<\/p>\n

}<\/p>\n

Note that now that we’ve declared toppings to be an array of strings, TypeScript will enforce this. If we try to assign a number to it, we will get an error at compilation time.<\/p>\n

If you want to have a property that can be set to a value of any type, however, you can still do this: just declare its type to be “any”:<\/p>\n

class Pizza {<\/p>\n

toppings: any;<\/p>\n

\/\/…<\/p>\n

}<\/p>\n

Typings<\/h4>\n

Astute readers might be wondering what happens when TypeScript programmers need to interface with JavaScript modules that have no type information. TypeScript recognizes files labelled *.d.ts as definition files. These files are meant to use TypeScript to describe interfaces presented by JavaScript libraries.<\/p>\n

There are communities of people dedicated to creating typings for JavaScript projects. There is also a utility called typings (npm install –save-dev typings) that can be used to manage third party typings from a variety of sources. (Deprecated in TypeScript 2.0)<\/p>\n

In TypeScript 2.0, users can get type files directly from @types through npm (for example, npm install –save @types\/lodash will install lodash type file).<\/p>\n

Linting<\/h4>\n

Many editors support the concept of “linting” – a grammar check for computer programs. Linting can be done in a programmer’s editor and\/or through automation.<\/p>\n

For TypeScript there is a package called tslint, (npm install –save-dev tslint) which can be plugged into many editors. tslint can also be configured with a tslint.json file.<\/p>\n

Webpack can run tslint before it attempts to run tsc. This is done by installing tslint-loader (npm install –save-dev tslint-loader) which plugs into webpack like so:<\/p>\n

\/\/ ...\n\nmodule: {\n\n  preLoaders: [\n\n    { test: \/\\.ts$\/, loader: 'tslint' }\n\n  ],\n\n  loaders: [\n\n    { test: \/\\.ts$\/, loader: 'ts', exclude: \/node_modules\/ },\n\n    \/\/ ...\n\n  ]\n\n  \/\/ ...\n\n}<\/pre>\n\n\n
Go back to Tutorial<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
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