Adds checks for failure.

main.js

@@ -13,50 +13,46 @@ const btnGo_onClick = () => {
 
 const btnUp_onClick = () => {
     const grid = globals.grid;
-    if (canSlideUp(grid)) {
-        slideUp(grid);
+    if (slideUp(grid)) {
         addRandomTile();
         redraw(grid)
     } else {
         alert('Unable to slide Up.');
     }
-    // alert('Up');
+    checkForEnd(grid);
 }
 
 const btnDown_onClick = () => {
     const grid = globals.grid;
-    if (canSlideDown(grid)) {
-        slideDown(grid);
+    if (slideDown(grid)) {
         addRandomTile();
         redraw(grid)
     } else {
         alert('Unable to slide Down.');
     }
-    // alert('Down');
+    checkForEnd(grid);
 }
 
 const btnLeft_onClick = () => {
     const grid = globals.grid;
-    if (canSlideLeft(grid)) {
-        slideLeft(grid);
+    if (slideLeft(grid)) {
         addRandomTile();
         redraw(grid)
     } else {
         alert('Unable to slide Left.');
     }
-    // alert('Left');
+    checkForEnd(grid);
 }
 
 const btnRight_onClick = () => {
     const grid = globals.grid;
-    if (canSlideRight(grid)) {
-        slideRight(grid);
+    if (slideRight(grid)) {
         addRandomTile();
         redraw(grid)
     } else {
         alert('Unable to slide Right.');
     }
-    // alert('Right');
+    checkForEnd(grid);
 }
 
 const drawGrid = (grid, element) => {
@@ -139,6 +135,7 @@ const redraw = (grid) => {
 }
 
 const slideUp = (grid) => {
+    let didIDoIt = false;
     for (let columnIndex = 0; columnIndex < grid.numColumns; columnIndex++) {
         lastIndex = -1;
         for (let rowIndex = 0; rowIndex < grid.numRows; rowIndex++) {
@@ -147,13 +144,16 @@ const slideUp = (grid) => {
                 lastIndex++;
                 if (lastIndex != rowIndex) {
                     grid.swapTiles(rowIndex, columnIndex, lastIndex, columnIndex);
+                    didIDoIt = true;
                 }
             }
         }
     }
+    return didIDoIt;
 }
 
 const slideLeft = (grid) => {
+    let didIDoIt = false;
     for (let rowIndex = 0; rowIndex < grid.numRows; rowIndex++) {
         lastIndex = -1;
         for (let columnIndex = 0; columnIndex < grid.numColumns; columnIndex++) {
@@ -162,13 +162,16 @@ const slideLeft = (grid) => {
                 lastIndex++;
                 if (lastIndex != columnIndex) {
                     grid.swapTiles(rowIndex, columnIndex, rowIndex, lastIndex);
+                    didIDoIt = true;
                 }
             }
         }
     }
+    return didIDoIt;
 }
 
 const slideDown = (grid) => {
+    let didIDoIt = false;
     for (let columnIndex = 0; columnIndex < grid.numColumns; columnIndex++) {
         lastIndex = grid.numRows;
         for (let rowIndex = grid.numRows - 1; rowIndex >= 0; rowIndex -= 1) {
@@ -177,13 +180,16 @@ const slideDown = (grid) => {
                 lastIndex--;
                 if (lastIndex != rowIndex) {
                     grid.swapTiles(rowIndex, columnIndex, lastIndex, columnIndex);
+                    didIDoIt = true;
                 }
             }
         }
     }
+    return didIDoIt;
 }
 
 const slideRight = (grid) => {
+    let didIDoIt = false;
     for (let rowIndex = 0; rowIndex < grid.numRows; rowIndex++) {
         lastIndex = grid.numColumns;
         for (let columnIndex = grid.numColumns - 1; columnIndex >= 0; columnIndex -= 1) {
@@ -192,10 +198,12 @@ const slideRight = (grid) => {
                 lastIndex--;
                 if (lastIndex != columnIndex) {
                     grid.swapTiles(rowIndex, columnIndex, rowIndex, lastIndex);
+                    didIDoIt = true;
                 }
             }
         }
     }
+    return didIDoIt;
 }
 
 const canSlideUp = (grid) => {
@@ -267,3 +275,15 @@ const canSlideRight = (grid) => {
     return canIDoIt;
 }
 
+const gameIsLost = (grid) => {
+    return !canSlideUp(grid)
+        && !canSlideRight(grid)
+        && !canSlideDown(grid)
+        && !canSlideLeft(grid);
+}
+
+const checkForEnd = (grid) => {
+    if (gameIsLost(grid)) {
+        alert('A loser is you!');
+    }
+}