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TypeScript is transpiled into JavaScript using a compiler. TypeScript being converted into JavaScript means it runs anywhere that JavaScript runs!
TypeScript has an official compiler which can be installed through npm. Learn more about npm, and how to get started here:
Within your npm project, run the following command to install the compiler:
Example npm install typescript --save-dev Which should give you an output similar to:
Example added 1 package, and audited 2 packages in 2s found 0 vulnerabilities The compiler is installed in the node_modules directory and can be run with: npx tsc.
Which should give you an output similar to:
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Version 4.5.5 tsc: The TypeScript Compiler - Version 4.5.5Followed by a list of all the Common Commands.
Installing TypeScript globally means adding the tsc command to your system
so it is available from any folder.
Example npm install -g typescript
Example tsc -v
Quick access to tsc from any project or directory.
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Useful for trying commands, learning, or one - off scripts.Some editors or tools can discover a global compiler automatically.Different machines (or teammates) may have different global versions.Can drift from the version your project expects, causing subtle issues. May require elevated permissions on some systems to install globally.
Best practice is to install TypeScript as a project devDependency and run it with npx tsc so the exact version is consistent across environments. A global install is optional and convenient for ad-hoc usage.By default the TypeScript compiler will print a help message when run in an empty project.The compiler can be configured using a tsconfig.json file. You can have TypeScript create tsconfig.json with the recommended settings with:
Example npx tsc --init Which should give you an output similar to:
Created a new tsconfig.json with: TS target: es2016 module: commonjs strict: true esModuleInterop: true skipLibCheck: true forceConsistentCasingInFileNames: true
Here is an example of more things you could add to the tsconfig.json file:
{
"include": ["src"],
"compilerOptions": {
"outDir": "./build"
}
}You can open the file in an editor to add those options. This will configure the TypeScript compiler to transpile TypeScript files located in the src/ directory of your project, into JavaScript files in the build/ directory.
Let's create a simple "Hello, World!" program to verify your TypeScript setup. Create a new file named hello.ts with the following content:
hello.ts function greet(name: string): string {
return `Hello, ${name}!`;
}
const message: string = greet("World");
console.log(message);Example npx tsc hello.ts This will generate a hello.js file in the same directory:
Example function greet(name) {
return "Hello, ".concat(name, "!");
}
const message = greet("World");
console.log(message);Example node hello.js
Hello, World!
If you're using the tsconfig.json configuration mentioned earlier, you would place your TypeScript files in the src directory and the compiled JavaScript will appear in the build directory.