Create 红绿灯.js

红绿灯.js

@@ -0,0 +1,35 @@
+//用js写一个简单的交通灯功能，10秒绿灯倒数，3秒黄灯倒数，5秒红灯倒数，如何让三个灯不断交替重复？
+function red() {
+    console.log('red light');
+}
+
+function green() {
+    console.log('green light');
+}
+
+function yellow() {
+    console.log('yellow light');
+}
+function tick(timer, callback){
+    return new Promise((resolve, reject) => {
+        setTimeout(() => {
+            callback();
+            resolve();
+        }, timer);
+    });
+}
+var promise = new Promise((resolve, reject) => {
+	resolve() 
+});
+function loop() {
+    promise.then(() => {
+        return tick(10000, green);
+    }).then(() => {
+        return tick(3000, yellow);
+    }).then(() => {
+        return tick(5000, red);
+    }).then(() => {
+        loop();
+    });
+}
+loop();