Change parameter order to simplify signature

Author: wooorm

index.js

@@ -1,22 +1,13 @@
 import {visit} from 'unist-util-visit'
 
 export class Index {
-  constructor(tree, filter, prop) {
-    var pluck = (node) => node[prop]
-
-    if (prop === null || prop === undefined) {
-      if (filter === null || filter === undefined) {
-        prop = tree
-        tree = null
-      } else {
-        prop = filter
-      }
-
+  constructor(prop, tree, filter) {
+    if (filter === null || filter === undefined) {
       filter = trueConst
     }
 
     this.index = new Map()
-    this.keyfn = typeof prop === 'string' ? pluck : prop
+    this.keyfn = typeof prop === 'string' ? (node) => node[prop] : prop
 
     if (tree) {
       visit(tree, filter, (node) => this.add(node))

readme.md

@@ -34,12 +34,12 @@ var Index = require('unist-util-index')
 var tree = remark.parse(fs.readFileSync('readme.md'))
 
 // Index on heading depth:
-var index = new Index(tree, 'heading', 'depth')
+var index = new Index('depth', tree, 'heading')
 
 console.log(index.get(2).map(toString))
 
 // Index on definition identifier:
-index = new Index(tree, 'definition', 'identifier')
+index = new Index('identifier', tree, 'definition')
 
 console.log(index.get('unist').map(node => node.url))
 ```
@@ -56,28 +56,22 @@ Yields:
 This package exports the following identifiers: `Index`.
 There is no default export.
 
-### `class Index([tree[, test], ]prop|keyFn)`
+### `class Index(prop|keyFn[, tree[, test]])`
 
 Create an index data structure that maps keys (calculated by `keyFn` function or
 the values at `prop` in each node) to a list of nodes.
 
 If `tree` is given, the index is initialized with all nodes, optionally filtered
 by `test`.
 
-###### Signatures
-
-*   `new Index(prop|keyFn)`
-*   `new Index(tree, prop|keyFn)`
-*   `new Index(tree, test, prop|keyFn)`
-
 ###### Parameters
 
-*   `tree` ([`Node?`][node]) — [Tree][] to index
-*   `test` ([`Test`][is], optional) — [`is`][is]-compatible test (such as a
-    [type][])
 *   `prop` (`string`) — Property to look up in each node to find keys
 *   `keyFn` ([`Function`][keyfn]) — Function called with each node to calculate
     keys
+*   `tree` ([`Node?`][node]) — [Tree][] to index
+*   `test` ([`Test`][is], optional) — [`is`][is]-compatible test (such as a
+    [type][])
 
 ###### Returns
 

test.js

@@ -25,20 +25,20 @@ test('Index', function (t) {
     'new Index(keyFn)'
   )
 
-  instance = new Index(tree, 'id')
+  instance = new Index('id', tree)
 
   t.deepEqual(
     [instance instanceof Index, instance.get(1)],
     [true, [node, alt]],
-    'new Index(tree, prop)'
+    'new Index(prop, tree)'
   )
 
-  instance = new Index(tree, filter, 'id')
+  instance = new Index('id', tree, filter)
 
   t.deepEqual(
     [instance instanceof Index, instance.get(1)],
     [true, [node]],
-    'new Index(tree, filter, prop)'
+    'new Index(prop, tree, filter)'
   )
 
   t.end()
@@ -56,7 +56,7 @@ test('index.add', function (t) {
   var ast = u('root', [u('node', {word: 'foo'}), u('node', {word: 'bar'})])
   var extraNode = u('node', {word: 'foo'})
 
-  var index = new Index(ast, 'word')
+  var index = new Index('word', ast)
   t.deepEqual(index.get('foo'), [select('[word=foo]', ast)])
 
   var result = index.add(extraNode)
@@ -98,7 +98,7 @@ test('index.get', function (t) {
       ])
     ])
 
-    var index = new Index(ast, 'color')
+    var index = new Index('color', ast)
 
     st.deepEqual(index.get('black'), [
       select('[id=0]', ast),
@@ -132,7 +132,7 @@ test('index.get', function (t) {
         u('node', {word: 'constructor', id: 1}),
         u('node', {word: 'toString', id: 2})
       ])
-      var index = new Index(ast, 'word')
+      var index = new Index('word', ast)
 
       sst.deepEqual(index.get('__proto__'), [select('[id=0]', ast)])
       sst.deepEqual(index.get('constructor'), [select('[id=1]', ast)])
@@ -151,7 +151,7 @@ test('index.get', function (t) {
         u('node', {word: id1, id: 4}),
         u('node', {word: id2, id: 5})
       ])
-      var index = new Index(ast, 'word')
+      var index = new Index('word', ast)
 
       sst.deepEqual(index.get(false), [select('[id=0]', ast)])
       sst.deepEqual(index.get('false'), [select('[id=1]', ast)])
@@ -167,7 +167,7 @@ test('index.get', function (t) {
   })
 
   t.test('empty index', function (st) {
-    st.deepEqual(new Index(null, 'foo').get('bar'), [])
+    st.deepEqual(new Index('foo', null).get('bar'), [])
     st.deepEqual(new Index('foo').get('bar'), [])
     st.end()
   })
@@ -181,14 +181,14 @@ test('index.get', function (t) {
     ])
 
     st.test('type test', function (sst) {
-      var index = new Index(ast, 'node', 'word')
+      var index = new Index('word', ast, 'node')
       sst.deepEqual(index.get('foo'), [select('node[word="foo"]', ast)])
       sst.deepEqual(index.get('bar'), [select('node[word="bar"]', ast)])
       sst.end()
     })
 
     st.test('function test', function (sst) {
-      var index = new Index(ast, filter, 'word')
+      var index = new Index('word', ast, filter)
       sst.deepEqual(index.get('foo'), [select('node[word="foo"]', ast)])
       sst.deepEqual(index.get('bar'), [select('node[word="bar"]', ast)])
       sst.end()
@@ -210,7 +210,7 @@ test('index.get', function (t) {
     ])
     var index
 
-    index = new Index(ast, xPlusY)
+    index = new Index(xPlusY, ast)
     st.deepEqual(index.get(4), [
       select('[id=0]', ast),
       select('[id=2]', ast),
@@ -219,7 +219,7 @@ test('index.get', function (t) {
     st.deepEqual(index.get(0), [])
     st.deepEqual(index.get(5), [select('[id=1]', ast), select('[id=4]', ast)])
 
-    st.deepEqual(new Index(ast, 'node', xPlusY).get(4), [
+    st.deepEqual(new Index(xPlusY, ast, 'node').get(4), [
       select('[id=2]', ast),
       select('[id=3]', ast)
     ])
@@ -241,7 +241,7 @@ test('index.remove', function (t) {
     u('node', {word: 'bar'})
   ])
 
-  var index = new Index(ast, 'word')
+  var index = new Index('word', ast)
   t.deepEqual(index.get('foo'), [
     select('bad[word=foo]', ast),
     select('node[word=foo]', ast)