html代码：
<!doctype html>
Sliding Puzzle
<br> .picture {<br> border: 1px solid black;<br> }<br>
Sliding Puzzle
js代码：var context = document.getElementById('puzzle').getContext('2d');
var img = new Image();
img.src = './img/dimetrodon.jpg';
img.addEventListener('load', drawTiles, false);
var boardSize = document.getElementById('puzzle').width;
var tileCount = document.getElementById('scale').value;
var tileSize = boardSize / tileCount;
var clickLoc = new Object;
clickLoc.x = 0;
clickLoc.y = 0;
var emptyLoc = new Object;
emptyLoc.x = 0;
emptyLoc.y = 0;
var solved = false;
var boardParts = new Object;
setBoard();
document.getElementById('scale').onchange = function() {
tileCount = this.value;
tileSize = boardSize / tileCount;
setBoard();
drawTiles();
};
document.getElementById('puzzle').onmousemove = function(e) {
clickLoc.x = Math.floor((e.pageX - this.offsetLeft) / tileSize);
clickLoc.y = Math.floor((e.pageY - this.offsetTop) / tileSize);
};
document.getElementById('puzzle').onclick = function() {
if (distance(clickLoc.x, clickLoc.y, emptyLoc.x, emptyLoc.y) == 1) {
slideTile(emptyLoc, clickLoc);
drawTiles();
}
if (solved) {
setTimeout(function() {alert("You solved it!");}, 500);
}
};
function setBoard() {
boardParts = new Array(tileCount);
for (var i = 0; i < tileCount; ++i) {
boardParts[i] = new Array(tileCount);
for (var j = 0; j < tileCount; ++j) {
boardParts[i][j] = new Object;
boardParts[i][j].x = (tileCount - 1) - i;
boardParts[i][j].y = (tileCount - 1) - j;
}
}
emptyLoc.x = boardParts[tileCount - 1][tileCount - 1].x;
emptyLoc.y = boardParts[tileCount - 1][tileCount - 1].y;
solved = false;
}
function drawTiles() {
context.clearRect ( 0 , 0 , boardSize , boardSize );
for (var i = 0; i < tileCount; ++i) {
for (var j = 0; j < tileCount; ++j) {
var x = boardParts[i][j].x;
var y = boardParts[i][j].y;
if(i != emptyLoc.x || j != emptyLoc.y || solved == true) {
context.drawImage(img, x * tileSize, y * tileSize, tileSize, tileSize,
i * tileSize, j * tileSize, tileSize, tileSize);
}
}
}
}
function distance(x1, y1, x2, y2) {
return Math.abs(x1 - x2) + Math.abs(y1 - y2);
}
function slideTile(toLoc, fromLoc) {
if (!solved) {
boardParts[toLoc.x][toLoc.y].x = boardParts[fromLoc.x][fromLoc.y].x;
boardParts[toLoc.x][toLoc.y].y = boardParts[fromLoc.x][fromLoc.y].y;
boardParts[fromLoc.x][fromLoc.y].x = tileCount - 1;
boardParts[fromLoc.x][fromLoc.y].y = tileCount - 1;
// var a = toLoc.x;
// var b = toLoc.y;
toLoc.x = fromLoc.x;
toLoc.y = fromLoc.y;
// fromLoc.x = a;
// fromLoc.y = b;//这边为什么不用给emptyLoc改变坐标？
checkSolved();
}
}
function checkSolved() {
var flag = true;
for (var i = 0; i < tileCount; ++i) {
for (var j = 0; j < tileCount; ++j) {
if (boardParts[i][j].x != i || boardParts[i][j].y != j) {
flag = false;
}
}
}
solved = flag;
}
请问为什么js中的emptyLoc的x和y不需要更新，或者他的x和y是怎么更新的，他代码里面emptyLoc.x和emptyLoc.y的值貌似都是2，没有变化，不更新的话没办法继续判断距离distance==1啊，为什么它程序可以正确运行，还是我理解错了？
