feat: homework

index.js

@@ -1,22 +1,47 @@
 function myPromise(constructor) {
   let self = this;
 
-  self.status = "pending" //定义状态改变前的初始状态
+  self.status = "pending" //定义状态改变前的初始状态 pending resolved rejected
 
   self.value = undefined;//定义状态为resolved的时候的状态
 
   self.reason = undefined;//定义状态为rejected的时候的状态
 
-  function resolve(value) {
-
-    // TODO resolve如何改变状态及返回结果
+  self.resolveFnArr = [];
+  self.rejectFnArr = [];
+
+  function changeStatus(status, value) {
+    if (self.status !== 'pending') {
+      return;
+    }
+    self.status = status;
+    self.value = value;
+    let fnArr = self.status === 'resolved' ? self.resolveFnArr : self.rejectFnArr;
+    if (fnArr.length > 0) {
+      fnArr.forEach(item => {
+        item(value);
+      });
+    }
+  }
 
+  function resolve(value) {
+    if (self.resolveFnArr.length > 0) {
+      changeStatus('resolved', value);
+    }
+    let timer = setTimeout(() => {
+      changeStatus('resolved', value);
+      clearTimeout(timer);
+    }, 0)
   }
 
   function reject(reason) {
-
-    // TODO reject如何改变状态及返回结果
-
+    if (self.rejectFnArr.length > 0) {
+      changeStatus('rejected', reason);
+    }
+    let timer = setTimeout(() => {
+      changeStatus('rejected', reason);
+      clearTimeout(timer);
+    }, 0);
   }
 
   //捕获构造异常
@@ -34,8 +59,49 @@ function myPromise(constructor) {
 }
 
 myPromise.prototype.then = function (onFullfilled, onRejected) {
+  if (typeof onFullfilled !== 'function') {
+    onFullfilled = (res) => {
+      return res;
+    }
+  }
+  if (typeof onRejected !== 'function') {
+    onRejected = (reason) => {
+      return new myPromise((_, reject) => {
+        reject(reason);
+      })
+    }
+  }
+  return new myPromise((resolve, reject) => {
+    this.resolveFnArr.push((res) => {
+      try {
+        let excuteRes = onFullfilled(res);
+        if (excuteRes instanceof myPromise) {
+          excuteRes.then(resolve, reject);
+        } else {
+          resolve(excuteRes);
+        }
+      } catch (error) {
+        reject(error);
+      }
+    });
+    this.rejectFnArr.push((reason) => {
+      try {
+        let excuteRes = onRejected(reason);
+        if (excuteRes instanceof myPromise) {
+          excuteRes.then(resolve, reject);
+        } else {
+          resolve(excuteRes);
+        }
+      } catch (error) {
+        reject(error);
+      }
+    });
+  })
+}
 
-  //TODO then如何实现
-
+myPromise.prototype.catch = function (rejectFn) {
+  return this.then(null, rejectFn);
 }
-module.exports = myPromise
+
+
+module.exports = myPromise;

index.test.js

@@ -1,9 +1,25 @@
 const myPromise = require('./index');
 
-var p = new myPromise(function (resolve, reject) { resolve('isOk') });
-test('测试primose的then是否成功', () => {
-  expect.assertions(1);
-  return p.then(data => {
-    expect(data).toBe('isOk');
+var ok = new myPromise(function (resolve, reject) { resolve('isOk') });
+var notOk = new myPromise(function (resolve, reject) { reject('isNotOk') });
+describe('promise', function () {
+  test('测试primose的then是否成功', () => {
+    expect.assertions(1);
+    return ok.then(data => {
+      return data;
+    }).then(data => {
+      expect(data).toBe('isOk');
+    });
   });
-});
+  test('测试primose的catch是否成功', () => {
+    expect.assertions(1);
+    return notOk
+      .then((res) => {
+        console.log('nothing');
+      })
+      .catch(data => {
+        expect(data).toBe('isNotOk');
+      });
+  });
+});
+