Add week1 prep-exercises

Week1/prep-exercises/1-catwalk-promises/index.js

@@ -5,36 +5,44 @@ const STEP_INTERVAL_MS = 50;
 const DANCE_TIME_MS = 5000;
 const DANCING_CAT_URL =
   'https://media1.tenor.com/images/2de63e950fb254920054f9bd081e8157/tenor.gif';
+const WALKING_CAT_URL = 'http://www.anniemation.com/clip_art/images/cat-walk.gif';
 
 function walk(img, startPos, stopPos) {
   return new Promise((resolve) => {
-    // Resolve this promise when the cat (`img`) has walked from `startPos` to
-    // `stopPos`.
-    // Make good use of the `STEP_INTERVAL_PX` and `STEP_INTERVAL_MS`
-    // constants.
+      let pos = startPos;
+      const timer = setInterval(() => {
+          pos += STEP_SIZE_PX;
+          img.style.left = `${pos}px`;
+          if (pos >= stopPos) {
+              clearInterval(timer);
+              resolve();
+          }
+      }, STEP_INTERVAL_MS);
   });
 }
 
 function dance(img) {
   return new Promise((resolve) => {
-    // Switch the `.src` of the `img` from the walking cat to the dancing cat
-    // and, after a timeout, reset the `img` back to the walking cat. Then
-    // resolve the promise.
-    // Make good use of the `DANCING_CAT_URL` and `DANCE_TIME_MS` constants.
+      const originalSrc = img.src;
+      img.src = DANCING_CAT_URL;
+      setTimeout(() => {
+          img.src = originalSrc;
+          resolve();
+      }, DANCE_TIME_MS);
   });
 }
 
-function catWalk() {
+async function catWalk() {
   const img = document.querySelector('img');
   const startPos = -img.width;
   const centerPos = (window.innerWidth - img.width) / 2;
   const stopPos = window.innerWidth;
 
-  // Use the `walk()` and `dance()` functions to let the cat do the following:
-  // 1. Walk from `startPos` to `centerPos`.
-  // 2. Then dance for 5 secs.
-  // 3. Then walk from `centerPos` to `stopPos`.
-  // 4. Repeat the first three steps indefinitely.
+  while (true) {
+      await walk(img, startPos, centerPos);
+      await dance(img);
+      await walk(img, centerPos, stopPos);
+  }
 }
 
 window.addEventListener('load', catWalk);