> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# JavaScript Multi-line Comment
A multi-line comment in JavaScript is a lexical construct that instructs the JavaScript engine's parser to ignore a specific sequence of characters during the tokenization phase. The syntax is defined by a starting delimiter `/*` and a terminating delimiter `*/`.
During lexical analysis, the parser evaluates multi-line comments as whitespace (specifically, as token separators) rather than performing zero-width removal. Because they do not simply disappear to merge adjacent characters, inserting a comment within a single identifier or keyword splits the token and results in a `SyntaxError`.
```javascript theme={"dark"}
/*
The parser ignores this sequence.
It can span multiple lines.
*/
let x = 10;
// Evaluates as: let total = 100 + 50;
let total = 100 + /* inline token separator */ 50;
// Evaluates as: let my Var = 1; (Throws SyntaxError)
let my/*comment*/Var = 1;
```
## Automatic Semicolon Insertion (ASI)
According to the ECMAScript specification, if a multi-line comment contains one or more line breaks, the parser treats the entire comment as a `LineTerminator` rather than standard whitespace. This distinction is critical because a `LineTerminator` can unexpectedly trigger Automatic Semicolon Insertion (ASI) when following restricted productions such as `return`, `break`, `continue`, `throw`, or `yield`.
```javascript theme={"dark"}
function evaluateASI() {
return /*
*/ true;
}
// The line break inside the comment acts as a LineTerminator.
// The parser applies ASI, evaluating the code as:
// return;
// true;
// The function returns `undefined` instead of `true`.
```
## Technical Limitations: Nesting
JavaScript multi-line comments cannot be nested. The lexical scanner reads the comment sequentially and terminates the comment block at the very first instance of the closing delimiter `*/`. If a multi-line comment contains another multi-line comment, the parser treats the inner comment's closing delimiter as the end of the outer comment. The parser then resumes standard tokenization for the remaining text, which results in a `SyntaxError` when it eventually encounters the outer comment's dangling closing delimiter.
```javascript theme={"dark"}
/*
Initiating outer comment block.
/*
Initiating inner comment block.
*/
// The parser resumes execution here.
// This is valid JavaScript, so it is successfully tokenized and evaluated.
let z = 5;
*/ // SyntaxError: Unexpected token '*'
```
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