feat:toypromise

index.js

@@ -7,18 +7,48 @@ function myPromise(constructor) {
 
   self.reason = undefined;//定义状态为rejected的时候的状态
 
+  self.callbacks = []; // 存储then中传入的参数
+
   function resolve(value) {
 
     // TODO resolve如何改变状态及返回结果
+    self.status = "resolved";
+    self.value = value;
+
+    self.callbacks.forEach(cb=>self._handler(cb))
+    return this;
 
   }
 
   function reject(reason) {
 
     // TODO reject如何改变状态及返回结果
+    self.status = "rejected";
+    self.reason = reason;
+
+    self.callbacks.forEach(cb=>self._handler(cb))
+    return this;
 
   }
 
+  self._handler  = function(cb) {
+    const {onFullfilled, onRejected, nextResolve, nextReject} = cb
+    if(self.status === "pending") {
+      this.callbacks.push(cb);
+      return;
+    }
+    try {
+      if(self.status === "resolved") {
+        self.value = onFullfilled(self.value)
+      } else if (self.status === "rejected") {
+        self.value = onRejected(self.reason);
+      }
+      nextResolve(self.value)
+    } catch(err) {
+      nextReject(err)
+    }
+  }
+
   //捕获构造异常
 
   try {
@@ -35,7 +65,14 @@ function myPromise(constructor) {
 
 myPromise.prototype.then = function (onFullfilled, onRejected) {
 
-  //TODO then如何实现
-
+  return new myPromise((nextResolve, nextReject) => {
+    this._handler({
+      onFullfilled,
+      onRejected,
+      nextResolve,
+      nextReject
+    })
+  })
 }
+
 module.exports = myPromise

index.test.js

@@ -6,4 +6,14 @@ test('测试primose的then是否成功', () => {
   return p.then(data => {
     expect(data).toBe('isOk');
   });
-});
+});
+
+test('测试primose的then的鏈式調用是否成功', () => {
+  expect.assertions(1);
+  return p.then(() => {
+    return "isfail"
+  }).then(data=>{
+    expect(data).toBe('isfail');
+    // throw new Error("reject");
+  })
+});