@ and */ in JavaScript Multiline Comments

While documenting JavaScript code using JSDoc, I stumbled upon an annoying issue. My attempts to include the /* symbol in the example code within a multiline comment caused the entire comment block to break. This happens because */ is recognized as the ending tag for a multiline comment in JavaScript.

You can see the problem clearly in the blow code block!

/**
 * Checks whether two permission strings are semantically equal or not.
 *
 * @example
 * // returns true
 * equals('a/b/c/d/allow', 'a/b/c/*⁣/*/d/allow');
 *
 * @returns {boolean} True in case of equality and false otherwise.
*/
const equals = (first: string, second: string) => {
    // function's logic
    // ...

    return true; // or false
}

The solution is surprisingly simple: insert a Unicode invisible separator character between * and /. This character acts as a stealthy spacer, preventing the JavaScript interpreter from recognizing the sequence as the end of a comment. You can find and copy this invisible character here.

The same problem happens if you use the @ symbol to put a JSDoc code example of a decorator. Because the @ symbol has a special meaning for JSDoc, it leads to unintended changes in the rendered documentation. Consider this snippet:

/**
 * A NestJS handler decorator that defines an access permission constraint and enforces it.
 *
 * @example
 * `⁣`⁣`ts
 * // the request only needs to be authenticated and doesn't need any specific permissions
 * @RequiresAccess()
 * Class MyController {}
 * `⁣`⁣`
*/
export const RequiresAccess = Reflector.createDecorator<
  PermissionPathGen | PermissionPathGen[]
>({
  transform(value) {
    return value == undefined ? MUST_BE_AUTHENTICATED : value;
  },
});

Solving this is the same as the previous problem, you need to put an invisible separator before the @.

Using @ and */ symbols inside JS multiline comments

Comments

More from this blog

Agentic Engineering Manifesto — Practical Principles for AI-Driven Development

A Practical Specification for Roles, Permissions, and Policy Decisions

Javascript's Tricky "This" Keyword and Why Arrow Functions Matter

Introducing keyv-upstash: Seamless Key-Value Storage for Serverless Redis

Fast and Simple NestJS App Deployment on Vercel

Command Palette

Comments

More from this blog