An import statement declares a dependency on another module. It makes an exported function, class, or value available under a name in the importing file. In JavaScript, a function imported from `./tax.js` can then be called like a locally defined function. section 4.5.3
Default and named imports
In `index.js`, `import calcTax from "./tax.js";` imports a default feature. For named exports, put the required names in braces: `import { printDetails, applyDiscount } from "./utils.js";`. A statement can combine both forms: `import calcTaxAndSum, { calculateTax } from "./tax.js";`. Named imports need only list features the file uses. section 4.5.3 section 4.5.5
The location after `from` matters. A path beginning with `.` or `..` points to a module in the project, relative to the importing file. Without that prefix, the import refers to a module outside the local project; where tools search for it depends on the framework and build tools. section 4.5.3
Write the path for the generated JavaScript
In a Node.js ECMAScript-module project, `src/index.ts` can use `import { sum } from "./calc.js";` even though the source file is `src/calc.ts`. Include the generated JavaScript file’s extension, not `.ts`: TypeScript does not rewrite import paths for the runtime. Set `"type": "module"` in `package.json` and configure the compiler for the intended module format. Otherwise, emitted import syntax can fail with `Cannot use import statement outside a module`. section 2.3.1 section 5.8
An import need not name a binding. In a React app, `import 'bootstrap/dist/css/bootstrap.css';` includes an installed stylesheet; the same entry file also imports React, the app component, and local CSS. section 20.1.2
