Expressive Code Example

Mar 31, 2026

By Goosequill

5 minutes read

Table of Contents

Expressive Code
Collapsible Sections
Line Numbers
1. Displaying line numbers per block
2. Changing the starting line number

Expressive Code
Collapsible Sections
Line Numbers
1. Displaying line numbers per block
2. Changing the starting line number

Here, we’ll explore how code blocks look using Expressive Code. The provided examples are based on the official documentation, which you can refer to for further details.

Expressive Code

Syntax Highlighting

Regular syntax highlighting

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console.log('This code is syntax highlighted!')

Rendering ANSI escape sequences

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ANSI colors:
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- Regular: Red Green Yellow Blue Magenta Cyan
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- Bold:    Red Green Yellow Blue Magenta Cyan
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- Dimmed:  Red Green Yellow Blue Magenta Cyan
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256 colors (showing colors 160-177):
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160 161 162 163 164 165
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166 167 168 169 170 171
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172 173 174 175 176 177
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Full RGB colors:
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ForestGreen - RGB(34, 139, 34)
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Text formatting: Bold Dimmed Italic Underline

Editor & Terminal Frames

Code editor frames

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console.log('Title attribute example')

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<div>File name comment example</div>

Terminal frames

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echo "This terminal frame has no title"

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Write-Output "This one has a title!"

Overriding frame types

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echo "Look ma, no frame!"

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# Without overriding, this would be a terminal frame
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function Watch-Tail { Get-Content -Tail 20 -Wait $args }
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New-Alias tail Watch-Tail

Text & Line Markers

Marking full lines & line ranges

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// Line 1 - targeted by line number
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// Line 2
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// Line 3
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// Line 4 - targeted by line number
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// Line 5
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// Line 6
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// Line 7 - targeted by range "7-8"
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// Line 8 - targeted by range "7-8"

Selecting line marker types (mark, ins, del)

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function demo() {
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  console.log('this line is marked as deleted')
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  // This line and the next one are marked as inserted
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  console.log('this is the second inserted line')
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  return 'this line uses the neutral default marker type'
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}

Adding labels to line markers

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<button
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  role="button"
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  {...props}
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  value={value}
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  className={buttonClassName}
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  disabled={disabled}
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  active={active}
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>
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  {children &&
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    !active &&
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    (typeof children === 'string' ? <span>{children}</span> : children)}
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</button>

Adding long labels on their own lines

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<button
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  role="button"
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  {...props}
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  value={value}
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  className={buttonClassName}
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  disabled={disabled}
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  active={active}
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>
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  {children &&
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    !active &&
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    (typeof children === 'string' ? <span>{children}</span> : children)}
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</button>

Using diff-like syntax

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this line will be marked as inserted
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this line will be marked as deleted
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this is a regular line

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--- a/README.md
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+++ b/README.md
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@@ -1,3 +1,4 @@
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+this is an actual diff file
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-all contents will remain unmodified
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 no whitespace will be removed either

Combining syntax highlighting with diff-like syntax

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function thisIsJavaScript() {
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  // This entire block gets highlighted as JavaScript,
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  // and we can still add diff markers to it!
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  console.log('Old code to be removed')
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  console.log('New and shiny code!')
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}

Marking individual text inside lines

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function demo() {
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  // Mark any given text inside lines
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  return 'Multiple matches of the given text are supported';
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}

Regular expressions

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console.log('The words yes and yep will be marked.')

Escaping forward slashes

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echo "Test" > /home/test.txt

Selecting inline marker types (mark, ins, del)

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function demo() {
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  console.log('These are inserted and deleted marker types');
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  // The return statement uses the default marker type
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  return true;
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}

Word Wrap

Configuring word wrap per block

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// Example with wrap
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function getLongString() {
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  return 'This is a very long string that will most probably not fit into the available space unless the container is extremely wide'
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}

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// Example with wrap=false
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function getLongString() {
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  return 'This is a very long string that will most probably not fit into the available space unless the container is extremely wide'
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}

Configuring indentation of wrapped lines

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// Example with preserveIndent (enabled by default)
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function getLongString() {
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  return 'This is a very long string that will most probably not fit into the available space unless the container is extremely wide'
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}

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// Example with preserveIndent=false
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function getLongString() {
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  return 'This is a very long string that will most probably not fit into the available space unless the container is extremely wide'
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}

Collapsible Sections

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// All this boilerplate setup code will be collapsed
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import { someBoilerplateEngine } from '@example/some-boilerplate'
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import { evenMoreBoilerplate } from '@example/even-more-boilerplate'
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const engine = someBoilerplateEngine(evenMoreBoilerplate())
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// This part of the code will be visible by default
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engine.doSomething(1, 2, 3, calcFn)
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function calcFn() {
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  // You can have multiple collapsed sections
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  const a = 1
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  const b = 2
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  const c = a + b
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  // This will remain visible
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  console.log(`Calculation result: ${a} + ${b} = ${c}`)
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  return c
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}
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// All this code until the end of the block will be collapsed again
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engine.closeConnection()
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engine.freeMemory()
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engine.shutdown({ reason: 'End of example boilerplate code' })

Line Numbers

Displaying line numbers per block

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// This code block will show line numbers
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console.log('Greetings from line 2!')
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console.log('I am on line 3')

// Line numbers are disabled for this block
console.log('Hello?')
console.log('Sorry, do you know what line I am on?')

Changing the starting line number

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console.log('Greetings from line 5!')
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console.log('I am on line 6')