我想编写一个在Javscript/HTML中,在HTML文件页上绘制蓝色和红色方块搅乱难题。当点击蓝色方块时,它们根据它们相对于红色方块的位置而移动。我写了一个方法,画出正方形并将它们命名为“blue1,blue2,blue3,red”等。但是,当我尝试找到名为“red”的正方形并使用getElementById("red")
并调用getBoundingClientRect()
时,出现错误HTML javascript函数来创建元素,但无法找到它与其他功能
trying to call
getBoundingClientRect()
on a null object.
我不确定为什么它会是null
,因为当我运行我的代码时,我可以看到名为“红色”的正方形。
这里是绘制正方形的代码:
var board = [["blue3", "blue2"],["blue1", "red"]];
var dim = 2;
var width = 50;
var height = 50;
// add the squares
function addSquares()
{
for(var i = 0; i < dim; i++)
{
for(var j = 0; j < dim; j++)
{
// create square
var label = j + i * dim;
var name = board[i][j];
var div = document.createElement(name);
div.style.width = width + "px";
div.style.height = height + "px";
div.style.left = width * j + "px";
div.style.top = height * i + "px";
div.style.position = "absolute";
// determine color of square
if(i != dim - 1 || j != dim - 1)
{
div.style.backgroundColor = "blue";
}
else
{
div.style.backgroundColor = "red";
}
document.getElementById("container").appendChild(div);
// do something when clicked
div.addEventListener("click", function(){getMove(this);});
}
}
}
这里是getMove()
,在代码中有一个错误,一旦我打电话VAR red = redelem.getBoundingClientRect();
function getMove(elem) {
var move = elem.getBoundingClientRect();
var redelem = document.getElementById('red');
var red = redelem.getBoundingClientRect();
mwcenter = 0.5 * (move.right + move.left);
mhcenter = 0.5 * (move.bottom + move.top);
rwcenter = 0.5 * (red.right + red.left);
rhcenter = 0.5 * (red.bottom + red.top);
if (mwcenter - rwcenter == 50 && mhcenter == rhcenter)
{
leftPress(elem);
rightPress(redelem);
}
else if (mwcenter - rwcenter == -50 && mhcenter == rhcenter)
{
rightPress(elem);
leftPress(redelem);
}
else if (mhcenter - rhcenter == 50 && mwcenter == rwcenter)
{
upPress(elem);
downPress(redelem);
}
else if (mhcenter - rhcenter == -50 && mwcenter == rwcenter)
{
downPress(elem);
upPress(redelem);
}
}
你从来没有给它一个id,因此得到元素sby id返回null。 –