Iterative .hasPrefix (replacing recursive)

20× faster, like `has`.

Author: anko

benchmark/hasPrefix.js

@@ -0,0 +1,14 @@
+const benchmark = require('benchmark')
+const AKM = require('../main.js')
+
+const letters = 'abcdefghijklmnopqrstuvwxyz'.split('')
+
+const lettersMap = new AKM()
+for (const x of letters) lettersMap.set(Array(100).fill(x), true)
+
+new benchmark.Suite()
+  .add('100-item hasPrefix', () => {
+    for (const x of letters) lettersMap.hasPrefix(Array(100).fill(x))
+  })
+  .on('cycle', ev => console.log(String(ev.target)))
+  .run()

main.js

@@ -78,7 +78,7 @@ class ArrayKeyedMap {
     this._size = 0
   }
 
-  hasPrefix (path) { return hasPrefix(path, this._root, this) }
+  hasPrefix (path) { return hasPrefix.call(this, path) }
 
   get [Symbol.toStringTag] () { return 'ArrayKeyedMap' }
 
@@ -175,16 +175,13 @@ function del (path) {
   return hadPreviousValue
 }
 
-const hasPrefix = (path, store) => {
-  switch (path.length) {
-    case 0:
-      return true
-    default: {
-      const [next, ...rest] = path
-      const nextStore = store.get(next)
-      return nextStore ? hasPrefix(rest, nextStore) : false
-    }
+function hasPrefix (path) {
+  let map = this._root
+  for (const item of path) {
+    map = map.get(item)
+    if (!map) return false
   }
+  return true
 }
 
 const entries = function * (path, store) {