text-keyword-highlight Edge Function — Content

text-keyword-highlight — Highlight Keywords in Text

Wraps keyword occurrences in text with configurable HTML tags. Handles case-insensitive matching, overlapping keywords (longest match wins), and safe HTML entity escaping.

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API

POST /api/text-keyword-highlight

Request body

Field	Type	Required	Default	Description
text	string	✅	—	The plain text to highlight keywords in
keywords	string[]	✅	—	Keywords or phrases to highlight
tag	string	❌	"mark"	HTML tag to wrap matches in
className	string	❌	—	Optional CSS class added to the wrapping tag
caseSensitive	boolean	❌	false	Whether matching is case-sensitive

Success response (200)

{
  "success": true,
  "data": {
    "html": "The <mark>quick</mark> brown <mark>fox</mark> jumps.",
    "matchCount": 2,
    "matchedKeywords": ["quick", "fox"]
  }
}

Error responses

Code	HTTP	When
INVALID_INPUT	400	Missing required field or wrong type
INTERNAL_ERROR	500	Unexpected processing error

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Usage

cURL

curl -X POST "$FUNCTION_URL/api/text-keyword-highlight" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "The quick brown fox jumps over the lazy dog",
    "keywords": ["quick", "fox", "lazy"],
    "tag": "mark",
    "className": "search-hit"
  }'

TypeScript / JavaScript (HTTP)

const response = await fetch(`${FUNCTION_URL}/api/text-keyword-highlight`, {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    text: 'Cloudflare Workers are fast and scalable.',
    keywords: ['Workers', 'fast'],
    caseSensitive: false,
  }),
});
const { data } = await response.json();
console.log(data.html);
// Cloudflare <mark>Workers</mark> are <mark>fast</mark> and scalable.
console.log(data.matchCount); // 2

Direct import (Node / Bun / Deno)

import { keywordHighlight } from '@aerostack/functions/text-keyword-highlight';

const result = keywordHighlight({
  text: 'Build APIs fast with TypeScript and Hono.',
  keywords: ['APIs', 'TypeScript'],
  tag: 'span',
  className: 'highlight',
});
console.log(result.html);
// Build <span class="highlight">APIs</span> fast with <span class="highlight">TypeScript</span> and Hono.

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Use Cases

• Search result UIs: Highlight matching search terms in document excerpts and result snippets.
• Document review tools: Mark specified keywords in legal, medical, or compliance documents for review.
• Content moderation: Visually flag specific words or phrases in user-submitted content.
• AI output display: Highlight key entities or concepts identified by an LLM in the source text.

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Notes

• The input text is HTML-escaped before highlighting, so the output is safe to inject into HTML.
• When multiple keywords could match the same position, the longest keyword wins (e.g. "foo bar" takes priority over "foo" at the same position).
• matchedKeywords returns only keywords that were actually found — useful for showing "no results for X" messages.
• Empty strings in the keywords array are silently ignored.