code-block-writer

What is code-block-writer?

The code-block-writer npm package is a utility for generating code with proper formatting, such as indentation and line breaks. It is particularly useful when writing code generators or transpilers that need to output human-readable code.

What are code-block-writer's main functionalities?

Writing code with automatic indentation and new lines

This feature allows you to write code blocks with automatic indentation management. The code sample demonstrates how to create a class with a constructor and a property.

const CodeBlockWriter = require('code-block-writer');
const writer = new CodeBlockWriter();
writer.writeLine('class MyClass {').indent(() => {
  writer.writeLine('constructor() {').indent(() => {
    writer.writeLine('this.myProperty = 1;');
  }).writeLine('}');
}).writeLine('}');
console.log(writer.toString());

Conditional writing

This feature enables writing parts of the code conditionally. In the code sample, 'someCondition' is only written if the 'condition' is true.

const writer = new CodeBlockWriter();
const condition = true;
writer.write('if (').conditionalWrite(condition, 'someCondition').writeLine(') {').indent(() => {
  writer.writeLine('doSomething();');
}).writeLine('}');
console.log(writer.toString());

Block indentation

This feature allows for easy indentation of entire blocks of code. The code sample shows how to write a function with multiple lines inside its body, all properly indented.

const writer = new CodeBlockWriter();
writer.writeLine('function myFunction() {').indentBlock(() => {
  writer.writeLine('let x = 10;').writeLine('return x;');
}).writeLine('}');
console.log(writer.toString());

Other packages similar to code-block-writer

prettier

Prettier is an opinionated code formatter that supports many languages and integrates with most editors. Unlike code-block-writer, which is used for generating code, Prettier formats existing code according to its style rules.

js-beautify

js-beautify is a package that can format HTML, CSS, and JavaScript. It is similar to Prettier in that it formats existing code. It is not specifically designed for code generation like code-block-writer.

recast

Recast is a JavaScript AST tool that allows you to parse your code, modify it, and then generate new code. It is more complex than code-block-writer as it deals with abstract syntax trees, but it can be used for similar code generation tasks.

README

code-block-writer

Code writer for JavaScript and TypeScript code.

With Deno:

deno add jsr:@david/code-block-writer

Or with Node:

npm install --save code-block-writer

Example

// import CodeBlockWriter from "code-block-writer"; // for npm
import CodeBlockWriter from "@david/code-block-writer";

const writer = new CodeBlockWriter({
  // optional options
  newLine: "\r\n",         // default: "\n"
  indentNumberOfSpaces: 2, // default: 4
  useTabs: false,          // default: false
  useSingleQuote: true     // default: false
});

writer.write("class MyClass extends OtherClass").block(() => {
  writer.writeLine(`@MyDecorator(1, 2)`);
  writer.write(`myMethod(myParam: any)`).block(() => {
    writer.write("return this.post(").quote("myArgument").write(");");
  });
});

console.log(writer.toString());

Outputs (using "\r\n" for newlines):

class MyClass extends OtherClass {
  @MyDecorator(1, 2)
  myMethod(myParam: any) {
    return this.post('myArgument');
  }
}

Methods

• block(block?: () => void) - Indents all the code written within and surrounds it in braces.
• inlineBlock(block?: () => void) - Same as block, but doesn't add a space before the first brace and doesn't add a newline at the end.
• getLength() - Get the current number of characters.
• writeLine(text: string) - Writes some text and adds a newline.
• newLine() - Writes a newline.
• newLineIfLastNot() - Writes a newline if what was written last wasn't a newline.
• blankLine() - Writes a blank line. Does not allow consecutive blank lines.
• blankLineIfLastNot() - Writes a blank line if what was written last wasn't a blank line.
• quote() - Writes a quote character.
• quote(text: string) - Writes text surrounded in quotes.
• indent(times?: number) - Indents the current line. Optionally indents multiple times when providing a number.
• indent(block?: () => void) - Indents a block of code.
• space(times?: number) - Writes a space. Optionally writes multiple spaces when providing a number.
• spaceIfLastNot() - Writes a space if the last was not a space.
• tab(times?: number) - Writes a tab. Optionally writes multiple tabs when providing a number.
• tabIfLastNot() - Writes a tab if the last was not a tab.
• write(text: string) - Writes some text.
• conditionalNewLine(condition: boolean) - Writes a newline if the condition is matched.
• conditionalBlankLine(condition: boolean) - Writes a blank line if the condition is matched.
• conditionalWrite(condition: boolean, text: string) - Writes if the condition is matched.
• conditionalWrite(condition: boolean, textFunc: () => string) - Writes if the condition is matched.
• conditionalWriteLine(condition: boolean, text: string) - Writes some text and adds a newline if the condition is matched.
• conditionalWriteLine(condition: boolean, textFunc: () => string) - Writes some text and adds a newline if the condition is matched.
• setIndentationLevel(indentationLevel: number) - Sets the current indentation level.
• setIndentationLevel(whitespaceText: string) - Sets the current indentation level based on the provided whitespace text.
• withIndentationLevel(indentationLevel: number, action: () => void) - Sets the indentation level within the provided action.
• withIndentationLevel(whitespaceText: string, action: () => void) - Sets the indentation level based on the provided whitespace text within the action.
• getIndentationLevel() - Gets the current indentation level.
• queueIndentationLevel(indentationLevel: number) - Queues an indentation level to be used once a new line is written.
• queueIndentationLevel(whitespaceText: string) - Queues an indentation level to be used once a new line is written based on the provided whitespace text.
• hangingIndent(action: () => void) - Writes the code within the action with hanging indentation.
• hangingIndentUnlessBlock(action: () => void) - Writes the code within the action with hanging indentation unless a block is written going from the first line to the second.
• closeComment() - Writes text to exit a comment if in a comment.
• unsafeInsert(pos: number, text: string) - Inserts text into the writer. This will not update the writer's state. Read more in its jsdoc.
• isInComment() - Gets if the writer is currently in a comment.
• isAtStartOfFirstLineOfBlock() - Gets if the writer is currently at the start of the first line of the text, block, or indentation block.
• isOnFirstLineOfBlock() - Gets if the writer is currently on the first line of the text, block, or indentation block.
• isInString() - Gets if the writer is currently in a string.
• isLastNewLine() - Gets if the writer last wrote a newline.
• isLastBlankLine() - Gets if the writer last wrote a blank line.
• isLastSpace() - Gets if the writer last wrote a space.
• isLastTab() - Gets if the writer last wrote a tab.
• getLastChar() - Gets the last character written.
• endsWith(text: string) - Gets if the writer ends with the provided text.
• iterateLastChars<T>(action: (char: string, index: number) => T | undefined): T | undefined - Iterates over the writer's characters in reverse order, stopping once a non-null or undefined value is returned and returns that value.
• iterateLastCharCodes<T>(action: (charCode: number, index: number) => T | undefined): T | undefined - A slightly faster version of iterateLastChars that doesn't allocate a string per character.
• getOptions() - Gets the writer options.
• toString() - Gets the string.

Other Features

• Does not indent within strings.
• Escapes newlines within double and single quotes created with .quote(text).

C# Version

See CodeBlockWriterSharp.