@babel/code-frame

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2023-12-01

Install

npm install --save-dev @babel/code-frame

Usage

import { codeFrameColumns } from '@babel/code-frame';

const rawLines = `class Foo {
  constructor()
}`;
const location = { start: { line: 2, column: 16 } };

const result = codeFrameColumns(rawLines, location, { /* options */ });

console.log(result);

  1 | class Foo {
> 2 |   constructor()
    |                ^
  3 | }

If the column number is not known, you may omit it.

You can also pass an end hash in location.

import { codeFrameColumns } from '@babel/code-frame';

const rawLines = `class Foo {
  constructor() {
    console.log("hello");
  }
}`;
const location = { start: { line: 2, column: 17 }, end: { line: 4, column: 3 } };

const result = codeFrameColumns(rawLines, location, { /* options */ });

console.log(result);

  1 | class Foo {
> 2 |   constructor() {
    |                 ^
> 3 |     console.log("hello");
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
> 4 |   }
    | ^^^
  5 | };

Options

`highlightCode`

boolean, defaults to false.

Toggles syntax highlighting the code as JavaScript for terminals.

`linesAbove`

number, defaults to 2.

Adjust the number of lines to show above the error.

`linesBelow`

number, defaults to 3.

Adjust the number of lines to show below the error.

`forceColor`

boolean, defaults to false.

Enable this to forcibly syntax highlight the code as JavaScript (for non-terminals); overrides highlightCode.

`message`

string, otherwise nothing

Pass in a string to be displayed inline (if possible) next to the highlighted location in the code. If it can't be positioned inline, it will be placed above the code frame.

1 | class Foo {
> 2 |   constructor()
  |                ^ Missing {
3 | };

Upgrading from prior versions

Prior to version 7, the only API exposed by this module was for a single line and optional column pointer. The old API will now log a deprecation warning.

The new API takes a location object, similar to what is available in an AST.

This is an example of the deprecated (but still available) API:

import codeFrame from '@babel/code-frame';

const rawLines = `class Foo {
  constructor()
}`;
const lineNumber = 2;
const colNumber = 16;

const result = codeFrame(rawLines, lineNumber, colNumber, { /* options */ });

console.log(result);

To get the same highlighting using the new API:

import { codeFrameColumns } from '@babel/code-frame';

const rawLines = `class Foo {
  constructor() {
    console.log("hello");
  }
}`;
const location = { start: { line: 2, column: 16 } };

const result = codeFrameColumns(rawLines, location, { /* options */ });

console.log(result);