TypeScript

TypeScript support varies depending on how you consume the project:

• Community Support: Limited to GitHub issues, Stack Overflow (typescript tag), and the #typescript Discord channel.
• Microsoft Product Integration: When included with a Microsoft product, TypeScript follows the Modern Support Policy.
• Visual Studio: Servicing fixes for TypeScript versions included in under-support releases of Visual Studio are limited to security fixes.
• Assisted Support: Professional support is available via the Microsoft assisted support team by opening a ticket.

The src/lib directory contains the type definitions for APIs that are part of the JavaScript language environment. These are categorized into three main domains:

1. ECMAScript language features: Standard JavaScript APIs (e.g., methods on Array) as defined in ECMA-262.
2. DOM APIs: APIs available in web browsers.
3. Intl APIs: Internationalization APIs scoped to Intl as defined in ECMA-402.

TypeScript follows specific criteria for adding new APIs to its library definitions to ensure stability:

• ECMAScript & Intl APIs: Proposals must be at Stage 3 or later in the TC39 process. You can verify completed proposals via the JavaScript finished proposals list or the Intl finished proposals list.
• DOM APIs: APIs must be available without prefixes or flags in at least two different browser engines (e.g., not just two different Chromium-based browsers).

TypeScript formatting requires two primary components:

1. A formatting context: An object containing user settings such as tab size, newline character, and other stylistic preferences.
2. A SourceFile: The parsed representation of the code to be formatted.

The output of a formatting operation is a collection of TextChange objects. Each object describes a specific modification to the source text by specifying the range to be replaced and the new content.

export interface TextChange {
    span: TextSpan; // start, length
    newText: string;
}

TypeScript is a language that adds optional types to JavaScript, enabling better tooling for large-scale applications. It compiles to standards-based JavaScript that runs on any browser, host, or OS.

To begin using TypeScript, you can:

• Use the TypeScript Playground to try it out in your browser.
• Follow the TypeScript in 5 minutes guide for a quick start.
• Consult the Programming handbook for in-depth documentation.

The TypeScript formatter is not exported publicly. It is an internal service used by the language service to handle operations that insert or modify code.

To utilize formatting capabilities, you must interact with the Language Server rather than calling the formatting APIs directly.

To report bugs or request new features, use GitHub issues. Before filing a new issue, search the existing issues to prevent duplicates.

For general questions and community help, use the following resources:

• Stack Overflow: Use the typescript tag.
• Discord: Join the #typescript channel.

Files in the DOM library ending in .generated.d.ts are automatically produced and should not be edited manually.

If you need to modify these files, you must instead make changes to the input files used by the TypeScript DOM library generator.

You can install TypeScript using npm. To install the latest stable version as a development dependency, use the standard install command. To test the latest nightly builds, use the @next tag.

# Install the latest stable version
npm install -D typescript

# Install nightly builds
npm install -D typescript@next

The TypeScript Server (TSServer) communicates using a JSON-RPC-like protocol consisting of three message types: request, response, and event.

• Request: Sent by the client to execute a command. It includes a seq (sequence number) and a command string. Arguments are provided in the arguments field.
• Response: Sent by the server in reply to a request. It includes the original request_seq, a success boolean, the command name, and a body containing the result if successful.
• Event: Sent by the server to notify the client of asynchronous occurrences. It includes an event name and an optional body.

{
  "seq": 1,
  "type": "request",
  "command": "status",
  "arguments": {}
}

A SemanticDiagnosticsBuilderProgram extends BuilderProgram by caching semantic diagnostics. This is useful for performance in incremental environments where you only want to re-calculate diagnostics for files that have changed or are affected by changes.

To iterate through affected files and retrieve their diagnostics one by one, use: getSemanticDiagnosticsOfNextAffectedFile(cancellationToken?, ignoreSourceFile?).

This method returns an AffectedFileResult<readonly Diagnostic[]>, which contains either the diagnostics and the affected SourceFile or Program, or undefined when iteration is complete.

while (true) {
  const result = semanticBuilder.getSemanticDiagnosticsOfNextAffectedFile();
  if (!result) break;
  
  const { result: diagnostics, affected } = result;
  console.log(`File ${affected.fileName} has ${diagnostics.length} diagnostics`);
}