feat: add promise all

Author: chachaxw

js/promise.js

@@ -0,0 +1,47 @@
+/*
+ * @Author: Chacha
+ * @Date: 2022-04-19 22:33:05
+ * @Last Modified by: Chacha
+ * @Last Modified time: 2022-04-19 22:40:07
+ */
+
+/**
+ * Promise 练习
+ *
+ */
+
+Promise.myAll = (promises) => {
+    return new Promise((resolve, reject) => {
+        let count = 0;
+        let result = [];
+        const length = promises.length;
+
+        promises.forEach((p, i) => {
+            Promise.resolve(p)
+                .then((res) => {
+                    count += 1;
+                    result[i] = res;
+
+                    if (count === length) {
+                        resolve(result);
+                    }
+                })
+                .catch(reject);
+        });
+    });
+};
+
+let p1 = Promise.resolve(1);
+let p2 = 2;
+let p3 = new Promise((resolve) => {
+    setTimeout(resolve, 100, 3);
+});
+// let p4 = Promise.reject("出错啦");
+
+Promise.myAll([p1, p2, p3])
+    .then((res) => {
+        console.log(res, "res--3");
+    })
+    .catch((err) => {
+        console.log("err", err);
+    });