Add JSDoc based types

.gitignore

@@ -1,4 +1,5 @@
 .DS_Store
+*.d.ts
 *.log
 coverage/
 node_modules/

index.js

@@ -1,17 +1,44 @@
-export function visitChildren(callback) {
-  return visitor
+/**
+ * @typedef {import('unist').Parent} Parent
+ * @typedef {import('unist').Node} Node
+ *
+ * @callback Visitor
+ * @param {Node} node
+ * @param {number} index
+ * @param {Parent} parent
+ * @returns {void}
+ *
+ * @callback Visit
+ * @param {Parent} node
+ * @returns {void}
+ */
 
-  // Visit `parent`, invoking `callback` for each child.
-  function visitor(parent) {
+/**
+ * Wrap `visitor` to be called for each child in the nodes later given to
+ * `visit`.
+ *
+ * @param {Visitor} visitor
+ * @returns {Visit}
+ */
+export function visitChildren(visitor) {
+  return visit
+
+  /**
+   * Visit `parent`, calling `visitor` for each child.
+   *
+   * @param {Parent} parent
+   * @returns {void}
+   */
+  function visit(parent) {
     var index = -1
     var children = parent && parent.children
 
     if (!children) {
-      throw new Error('Missing children in `parent` for `visitor`')
+      throw new Error('Missing children in `parent` for `visit`')
     }
 
     while (++index in children) {
-      callback(children[index], index, parent)
+      visitor(children[index], index, parent)
     }
   }
 }

package.json

@@ -24,22 +24,33 @@
   "sideEffects": false,
   "type": "module",
   "main": "index.js",
+  "types": "index.d.ts",
   "files": [
+    "index.d.ts",
     "index.js"
   ],
+  "dependencies": {
+    "@types/unist": "^2.0.0"
+  },
   "devDependencies": {
+    "@types/tape": "^4.0.0",
     "c8": "^7.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
+    "rimraf": "^3.0.0",
     "tape": "^5.0.0",
+    "type-coverage": "^2.0.0",
+    "typescript": "^4.0.0",
     "xo": "^0.38.0"
   },
   "scripts": {
+    "prepack": "npm run build && npm run format",
+    "build": "rimraf \"*.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "test-api": "node test.js",
     "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node test.js",
-    "test": "npm run format && npm run test-coverage"
+    "test": "npm run build && npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -60,5 +71,10 @@
     "plugins": [
       "preset-wooorm"
     ]
+  },
+  "typeCoverage": {
+    "atLeast": 100,
+    "detail": true,
+    "strict": true
   }
 }

readme.md

@@ -63,16 +63,16 @@ There is no default export.
 
 ### `visit = visitChildren(visitor)`
 
-Wrap [`visitor`][visitor] to be invoked for each [child][] in the nodes later
+Wrap [`visitor`][visitor] to be called for each [child][] in the nodes later
 given to [`visit`][visit].
 
 #### `function visitor(child, index, parent)`
 
-Invoked if [`visit`][visit] is called on a [parent][] node for each [child][].
+Called if [`visit`][visit] is called on a [parent][] node for each [child][].
 
 #### `function visit(parent)`
 
-Invoke [`visitor`][visitor] for each [child][] of the [parent][].
+Called [`visitor`][visitor] for each [child][] of the [parent][].
 
 ## Related
 

test.js

@@ -6,6 +6,7 @@ function noop() {}
 test('visitChildren()', function (t) {
   t.throws(
     function () {
+      // @ts-ignore runtime.
       visitChildren(noop)()
     },
     /Missing children in `parent`/,
@@ -14,22 +15,26 @@ test('visitChildren()', function (t) {
 
   t.throws(
     function () {
+      // @ts-ignore runtime.
       visitChildren(noop)({})
     },
     /Missing children in `parent`/,
     'should throw without parent'
   )
 
-  t.test('should invoke `fn` for each child in `parent`', function (st) {
-    var values = [0, 1, 2, 3]
-    var context = {}
+  t.test('should call `fn` for each child in `parent`', function (st) {
+    var children = [
+      {type: 'x', value: 0},
+      {type: 'x', value: 1},
+      {type: 'x', value: 2},
+      {type: 'x', value: 3}
+    ]
+    var context = {type: 'y', children}
     var n = -1
 
-    context.children = values
-
-    visitChildren(function (value, index, parent) {
+    visitChildren(function (child, index, parent) {
       n++
-      st.strictEqual(value, values[n])
+      st.strictEqual(child, children[n])
       st.strictEqual(index, n)
       st.strictEqual(parent, context)
     })(context)
@@ -38,19 +43,35 @@ test('visitChildren()', function (t) {
   })
 
   t.test('should work when new children are added', function (st) {
-    var values = [0, 1, 2, 3, 4, 5, 6]
+    var children = [
+      {type: 'x', value: 0},
+      {type: 'x', value: 1},
+      {type: 'x', value: 2},
+      {type: 'x', value: 3},
+      {type: 'x', value: 4},
+      {type: 'x', value: 5},
+      {type: 'x', value: 6}
+    ]
     var n = -1
 
-    visitChildren(function (value, index, parent) {
+    visitChildren(function (child, index, parent) {
       n++
 
       if (index < 3) {
-        parent.children.push(parent.children.length)
+        parent.children.push({type: 'x', value: parent.children.length})
       }
 
-      st.strictEqual(value, values[n])
-      st.strictEqual(index, values[n])
-    })({children: [0, 1, 2, 3]})
+      st.deepEqual(child, children[n])
+      st.deepEqual(index, n)
+    })({
+      type: 'y',
+      children: [
+        {type: 'x', value: 0},
+        {type: 'x', value: 1},
+        {type: 'x', value: 2},
+        {type: 'x', value: 3}
+      ]
+    })
 
     st.end()
   })

tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "include": ["*.js"],
+  "compilerOptions": {
+    "target": "ES2020",
+    "lib": ["ES2020"],
+    "module": "ES2020",
+    "moduleResolution": "node",
+    "allowJs": true,
+    "checkJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "allowSyntheticDefaultImports": true,
+    "skipLibCheck": true
+  }
+}