From b0b0208883af7e0fc6bfa1d5c6402dadc77a68a7 Mon Sep 17 00:00:00 2001
From: buzuosheng <1015350043@qq.com>
Date: Thu, 20 Jul 2023 18:52:26 +0800
Subject: [PATCH 1/2] intersection

---
 src/index.ts              | 1 +
 src/intersection.ts       | 5 +++++
 test/intersection.spec.ts | 8 ++++++++
 3 files changed, 14 insertions(+)
 create mode 100644 src/intersection.ts
 create mode 100644 test/intersection.spec.ts

diff --git a/src/index.ts b/src/index.ts
index a784ab6..efba292 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -33,3 +33,4 @@ export * from './compose'
 export * from './difference'
 export * from './async'
 export * from './nth'
+export * from './intersection'
\ No newline at end of file
diff --git a/src/intersection.ts b/src/intersection.ts
new file mode 100644
index 0000000..cc4c312
--- /dev/null
+++ b/src/intersection.ts
@@ -0,0 +1,5 @@
+export function intersection<T>(
+  ...list: T[][]
+): T[] {
+  return list.reduce((a, b) => a.filter(c => b.includes(c)));
+}
diff --git a/test/intersection.spec.ts b/test/intersection.spec.ts
new file mode 100644
index 0000000..59d62b0
--- /dev/null
+++ b/test/intersection.spec.ts
@@ -0,0 +1,8 @@
+import { intersection } from '../src'
+
+describe('isObject', function() {
+  let list = [['a', 'b','c'], ['a','c'], ['a'], ['a', 'd']]
+  it('should work', function() {
+    expect(intersection(...list)).toEqual(['a'])
+  })
+})

From 2da2b5461c850a1f6a793dcfd13099f5e5b6fc39 Mon Sep 17 00:00:00 2001
From: buzuosheng <1015350043@qq.com>
Date: Fri, 21 Jul 2023 14:55:51 +0800
Subject: [PATCH 2/2] intersectionBy

---
 src/intersection.ts       | 17 +++++++++++++----
 test/intersection.spec.ts | 19 ++++++++++++++++---
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/src/intersection.ts b/src/intersection.ts
index cc4c312..a190694 100644
--- a/src/intersection.ts
+++ b/src/intersection.ts
@@ -1,5 +1,14 @@
-export function intersection<T>(
-  ...list: T[][]
-): T[] {
-  return list.reduce((a, b) => a.filter(c => b.includes(c)));
+type by<T> = (item: T) => number | string
+
+export function intersection<T>(...args: Array<T[] | by<T>>): T[] {
+  if (!args || !args.length) return []
+  if (args.slice(0, args.length - 1).find(item => typeof item === 'function')) return []
+  const list: T[][] = args.filter(Array.isArray)
+  const by: by<T> = typeof args[args.length - 1] === 'function' ? args[args.length - 1] as by<T> : (x => x as number);
+  return list?.reduce((a, b) => {
+    const setB = new Set(b.map(by));
+    return a.filter(c => setB.has(by(c)));
+  });
 }
+
+export { intersection as intersectionBy }
diff --git a/test/intersection.spec.ts b/test/intersection.spec.ts
index 59d62b0..ebafd96 100644
--- a/test/intersection.spec.ts
+++ b/test/intersection.spec.ts
@@ -1,8 +1,21 @@
 import { intersection } from '../src'
+import { intersectionBy } from '../src'
 
-describe('isObject', function() {
-  let list = [['a', 'b','c'], ['a','c'], ['a'], ['a', 'd']]
-  it('should work', function() {
+describe('should work', function () {
+  let list = [['a', 'b', 'c'], ['a', 'c'], ['a'], ['a', 'd']]
+  it('should work', function () {
+    expect(intersection()).toEqual([])
+    expect(intersection([])).toEqual([])
+    expect(intersection([2, 1], [4, 2], [1, 2])).toEqual([2])
+    expect(intersection([2, 1])).toEqual([2, 1])
     expect(intersection(...list)).toEqual(['a'])
   })
+
+  it('should work with by', function () {
+    expect(intersectionBy()).toEqual([])
+    expect(intersectionBy([])).toEqual([])
+    expect(intersectionBy([{ 'x': 1 }])).toEqual([{ 'x': 1 }])
+    expect(intersectionBy([2, 1], [4, 2], [1, 2], Math.floor)).toEqual([2])
+    expect(intersectionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], x => x.x)).toEqual([{ 'x': 1 }])
+  })
 })