add 5.js

5.js

@@ -0,0 +1,76 @@
+let uid = 0;
+
+class Watcher {
+    constructor () {
+        this.id = ++uid;
+    }
+
+    update () {
+        console.log('watch' + this.id + ' update');
+        queueWatcher(this);
+    }
+
+    run () {
+        console.log('watch' + this.id + '视图更新啦～');
+    }
+}
+
+let callbacks = [];
+let pending = false;
+
+function flushCallbacks () {
+    pending = false;
+    const copies = callbacks.slice(0);
+    callbacks.length = 0;
+    for (let i = 0; i < copies.length; i++) {
+        copies[i]();
+    }
+}
+
+function nextTick (cb) {
+    callbacks.push(cb);
+
+    if (!pending) {
+        pending = true;
+        setTimeout(flushCallbacks, 0);
+    }
+}
+
+let has = {};
+let queue = [];
+let waiting = false;
+
+function flushSchedulerQueue () {
+    let watcher, id;
+
+    for (index = 0; index < queue.length; index++) {
+        watcher = queue[index]
+        id = watcher.id;
+        has[id] = null;
+        watcher.run();
+    }
+
+    waiting  = false;
+}
+
+function queueWatcher(watcher) {
+    const id = watcher.id;
+    if (has[id] == null) {
+        has[id] = true;
+        queue.push(watcher);
+
+        if (!waiting) {
+            waiting = true;
+            nextTick(flushSchedulerQueue);
+        }
+    }
+}
+
+(function () {
+    let watch1 = new Watcher();
+    let watch2 = new Watcher();
+
+    watch1.update();
+    watch1.update();
+    watch2.update();
+})();