Initialize map from an Iterable<[K, V]>

Author: dgraham

src/index.ts

@@ -1,6 +1,14 @@
 export default class MultiMap<K, V> {
   private map: Map<K, Set<V>> = new Map()
 
+  constructor(iterable?: Iterable<[K, V]>) {
+    if (iterable) {
+      for (const [k, v] of iterable) {
+        this.set(k, v)
+      }
+    }
+  }
+
   get(key: K): Set<V> {
     const values = this.map.get(key)
     return values ? values : new Set()

test/index.js

@@ -1,6 +1,16 @@
 import MultiMap from '../dist/index.js'
 
 describe('multimap', function () {
+  it('initializes from an iterable', function () {
+    const map = new MultiMap([
+      ['k1', 1],
+      ['k1', 2],
+      ['k2', 3]
+    ])
+    assert.deepEqual([1, 2], [...map.get('k1')])
+    assert.deepEqual([3], [...map.get('k2')])
+  })
+
   it('size measures keys not values', function () {
     const map = new MultiMap()
     assert.equal(0, map.size)