Use ESM

Closes GH-71.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>
Reviewed-by: Jonathan Haines <jonno.haines@gmail.com>

.gitignore

@@ -1,7 +1,4 @@
 .DS_Store
 *.log
-.nyc_output/
 coverage/
 node_modules/
-mdast-util-toc.js
-mdast-util-toc.min.js

example.js

@@ -1,16 +1,19 @@
+// remark-usage-ignore-next
+import {inspect} from 'util'
+
 // Dependencies:
-var u = require('unist-builder')
-var toc = require('.')
+import {u} from 'unist-builder'
+import {toc} from './index.js'
 
-// Given a mdast tree:
-var tree = u('root', [
+// Now running:
+const tree = u('root', [
   u('heading', {depth: 1}, [u('text', 'Alpha')]),
   u('heading', {depth: 2}, [u('text', 'Bravo')]),
   u('heading', {depth: 3}, [u('text', 'Charlie')]),
   u('heading', {depth: 2}, [u('text', 'Delta')])
 ])
 
-var table = toc(tree)
+const table = toc(tree)
 
 // Yields:
-console.log('javascript', require('util').inspect(table, {depth: 3}))
+console.log('javascript', inspect(table, {depth: 3}))

index.js

@@ -1,3 +1 @@
-'use strict'
-
-module.exports = require('./lib')
+export {toc} from './lib/index.js'

lib/contents.js

@@ -1,14 +1,10 @@
-'use strict'
-
-var extend = require('extend')
-
-module.exports = contents
+import extend from 'extend'
 
 // Transform a list of heading objects to a markdown list.
-function contents(map, tight, prefix, ordered) {
-  var table = {type: 'list', ordered: ordered, spread: false, children: []}
-  var minDepth = Number.POSITIVE_INFINITY
-  var index = -1
+export function contents(map, tight, prefix, ordered) {
+  const table = {type: 'list', ordered, spread: false, children: []}
+  let minDepth = Number.POSITIVE_INFINITY
+  let index = -1
 
   // Find minimum depth.
   while (++index < map.length) {
@@ -35,11 +31,11 @@ function contents(map, tight, prefix, ordered) {
 }
 
 // Insert an entry into `parent`.
+// eslint-disable-next-line max-params
 function insert(entry, parent, tight, prefix, ordered) {
-  var siblings = parent.children
-  var tail = siblings[siblings.length - 1]
-  var index = -1
-  var item
+  const siblings = parent.children
+  const tail = siblings[siblings.length - 1]
+  let index = -1
 
   if (entry.depth === 1) {
     siblings.push({
@@ -65,13 +61,13 @@ function insert(entry, parent, tight, prefix, ordered) {
     entry.depth--
     insert(entry, tail, tight, prefix, ordered)
   } else if (parent.type === 'list') {
-    item = {type: 'listItem', spread: false, children: []}
+    const item = {type: 'listItem', spread: false, children: []}
     siblings.push(item)
     insert(entry, item, tight, prefix, ordered)
   } else {
-    item = {
+    const item = {
       type: 'list',
-      ordered: ordered,
+      ordered,
       spread: false,
       children: []
     }
@@ -95,8 +91,8 @@ function insert(entry, parent, tight, prefix, ordered) {
 }
 
 function all(children) {
-  var result = []
-  var index = -1
+  let result = []
+  let index = -1
 
   if (children) {
     while (++index < children.length) {
@@ -108,8 +104,6 @@ function all(children) {
 }
 
 function one(node) {
-  var copy
-
   if (
     node.type === 'link' ||
     node.type === 'linkReference' ||
@@ -119,7 +113,7 @@ function one(node) {
     return all(node.children)
   }
 
-  copy = extend({}, node)
+  let copy = extend({}, node)
 
   delete copy.children
   delete copy.position

lib/index.js

@@ -1,29 +1,27 @@
-'use strict'
-
-module.exports = toc
-
-var search = require('./search')
-var contents = require('./contents')
-var toExpression = require('./to-expression')
+import {search} from './search.js'
+import {contents} from './contents.js'
+import {toExpression} from './to-expression.js'
 
 // Get a TOC representation of `node`.
-function toc(node, options) {
-  var settings = options || {}
-  var heading = settings.heading ? toExpression(settings.heading) : null
-  var result = search(node, heading, settings)
+export function toc(node, options) {
+  const settings = options || {}
+  const heading = settings.heading ? toExpression(settings.heading) : null
+  const result = search(node, heading, settings)
 
-  result.map = result.map.length
-    ? contents(
-        result.map,
-        settings.tight,
-        settings.prefix,
-        settings.ordered || false
-      )
-    : null
+  result.map =
+    result.map.length > 0
+      ? contents(
+          result.map,
+          settings.tight,
+          settings.prefix,
+          settings.ordered || false
+        )
+      : null
 
   // No given heading.
   if (!heading) {
-    result.endIndex = result.index = null
+    result.endIndex = null
+    result.index = null
   }
 
   return result

lib/search.js

@@ -1,21 +1,19 @@
-'use strict'
+import Slugger from 'github-slugger'
+import toString from 'mdast-util-to-string'
+import {visit} from 'unist-util-visit'
+import {convert} from 'unist-util-is'
+import {toExpression} from './to-expression.js'
 
-module.exports = search
-
-var toString = require('mdast-util-to-string')
-var visit = require('unist-util-visit')
-var convert = require('unist-util-is/convert')
-var slugs = require('github-slugger')()
-var toExpression = require('./to-expression')
+const slugs = new Slugger()
 
 // Search a node for a location.
-function search(root, expression, settings) {
-  var skip = settings.skip && toExpression(settings.skip)
-  var parents = convert(settings.parents || root)
-  var map = []
-  var index
-  var endIndex
-  var opening
+export function search(root, expression, settings) {
+  const skip = settings.skip && toExpression(settings.skip)
+  const parents = convert(settings.parents || root)
+  const map = []
+  let index
+  let endIndex
+  let opening
 
   slugs.reset()
 
@@ -25,16 +23,18 @@ function search(root, expression, settings) {
 
   return {
     index: index || -1,
+    // <sindresorhus/eslint-plugin-unicorn#980>
+    // eslint-disable-next-line unicorn/explicit-length-check
     endIndex: index ? endIndex || root.children.length : -1,
-    map: map
+    map
   }
 
   function onheading(node, position, parent) {
-    var value = toString(node)
-    /* istanbul ignore next - to do: remove this when `remark-attr` is up to
-     * date w/ micromark. */
-    var id = node.data && node.data.hProperties && node.data.hProperties.id
-    var slug = slugs.slug(id || value)
+    const value = toString(node)
+    // Remove this when `remark-attr` is up to date w/ micromark.
+    /* c8 ignore next */
+    const id = node.data && node.data.hProperties && node.data.hProperties.id
+    const slug = slugs.slug(id || value)
 
     if (!parents(parent)) {
       return

lib/to-expression.js

@@ -1,8 +1,4 @@
-'use strict'
-
-module.exports = toExpression
-
 // Transform a string into an applicable expression.
-function toExpression(value) {
+export function toExpression(value) {
   return new RegExp('^(' + value + ')$', 'i')
 }

package.json

@@ -25,10 +25,13 @@
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
     "Jonathan Haines <jonno.haines@gmail.com> (https://barrythepenguin.github.io)"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "types": "types/index.d.ts",
   "files": [
     "types/index.d.ts",
-    "lib",
+    "lib/",
     "index.js"
   ],
   "dependencies": {
@@ -37,13 +40,12 @@
     "extend": "^3.0.2",
     "github-slugger": "^1.2.1",
     "mdast-util-to-string": "^2.0.0",
-    "unist-util-is": "^4.0.0",
-    "unist-util-visit": "^2.0.0"
+    "unist-util-is": "^5.0.0",
+    "unist-util-visit": "^3.0.0"
   },
   "devDependencies": {
-    "browserify": "^17.0.0",
+    "c8": "^7.0.0",
     "dtslint": "^4.0.0",
-    "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "remark": "^13.0.0",
     "remark-attr": "^0.11.0",
@@ -54,27 +56,16 @@
     "remark-preset-wooorm": "^8.0.0",
     "remark-usage": "^9.0.0",
     "tape": "^5.0.0",
-    "tinyify": "^3.0.0",
     "typescript": "^4.0.0",
     "unified": "^9.0.0",
-    "unist-builder": "^2.0.0",
-    "xo": "^0.38.0"
+    "unist-builder": "^3.0.0",
+    "xo": "^0.39.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "build-bundle": "browserify . -s mdastUtilTOC > mdast-util-toc.js",
-    "build-mangle": "browserify . -s mdastUtilTOC -p tinyify > mdast-util-toc.min.js",
-    "build": "npm run build-bundle && npm run build-mangle",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test/index.js",
-    "test-types": "dtslint types",
-    "test": "npm run format && npm run build && npm run test-coverage && npm run test-types"
-  },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
+    "test-api": "node test/index.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node test/index.js",
+    "test": "npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -86,16 +77,16 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
-    "rules": {
-      "max-params": "off",
-      "no-multi-assign": "off",
-      "unicorn/explicit-length-check": "off",
-      "unicorn/prefer-optional-catch-binding": "off"
-    },
+    "overrides": [
+      {
+        "files": "example.js",
+        "rules": {
+          "capitalized-comments": "off"
+        }
+      }
+    ],
     "ignores": [
-      "types/",
-      "mdast-util-toc.js"
+      "types/"
     ]
   },
   "remarkConfig": {

readme.md

@@ -12,6 +12,9 @@
 
 ## Install
 
+This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
+Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+
 [npm][]:
 
 ```sh
@@ -23,21 +26,21 @@ npm install mdast-util-toc
 Dependencies:
 
 ```javascript
-var u = require('unist-builder')
-var toc = require('mdast-util-toc')
+import {u} from 'unist-builder'
+import {toc} from 'mdast-util-toc'
 ```
 
-Given a mdast tree:
+Now running:
 
 ```javascript
-var tree = u('root', [
+const tree = u('root', [
   u('heading', {depth: 1}, [u('text', 'Alpha')]),
   u('heading', {depth: 2}, [u('text', 'Bravo')]),
   u('heading', {depth: 3}, [u('text', 'Charlie')]),
   u('heading', {depth: 2}, [u('text', 'Delta')])
 ])
 
-var table = toc(tree)
+const table = toc(tree)
 ```
 
 Yields:
@@ -57,6 +60,9 @@ Yields:
 
 ## API
 
+This package exports the following identifiers: `toc`.
+There is no default export.
+
 ### `toc(tree[, options])`
 
 Generate a Table of Contents from a [tree][].