javascript - 单击时获取 Canvas 元素的 ID

Question

我想获取我点击的 Canvas 的ID，但是使用我编写的代码，我总是获取最后一个 Canvas 的ID。是否有可能获得多维数组的值？我应该将 onclick 事件放在 switch case 内吗？

function drawFigures(figures) {
    var frontDiv = document.createElement("div");
    frontDiv.setAttribute("id","frontDiv");
    document.getElementById('game').appendChild(frontDiv);

    for(var y=0; y<figures.length; y++) {
        fieldDiv = document.createElement("div");
        fieldDiv.setAttribute("class", "figureFieldDiv");
        frontDiv.appendChild(fieldDiv);

        for(var x=0; x<figures[y].length; x++) {
            var canvas = document.createElement("canvas");
            canvas.setAttribute("id", y+","+x);
            canvas.width = 20;
            canvas.height = 20;
            var ctx = canvas.getContext('2d');
            fieldDiv.appendChild(canvas);
            document.getElementById(y+","+x).onclick = function() {console.log(y+","+x)}, false;
            switch(figures[y][x]) {

                case 0:
                    break;
                case 1:
                    ctx.fillStyle = "#F00";
                    ctx.arc(canvas.width/3,canvas.width/3,canvas.width/3,0,360);
                    ctx.fill();
                    break;
                case 2:
                    ctx.fillStyle = "#0F0";
                    ctx.arc(canvas.width/3,canvas.width/3,canvas.width/3,0,360);
                    ctx.fill();
                    break;
                case 3:
                    ctx.fillStyle = "#FF0";
                    ctx.arc(canvas.width/3,canvas.width/3,canvas.width/3,0,360);
                    ctx.fill();
                    break;
                case 4:
                    ctx.fillStyle = "#00F";
                    ctx.arc(canvas.width/3,canvas.width/3,canvas.width/3,0,360);
                    ctx.fill();
                    break;
                case 5:
                    break;
                case 6:
                    ctx.fillStyle = "#0FF";
                    ctx.arc(canvas.width/3,canvas.width/3,canvas.width/3,0,360);
                    ctx.fill();
                    break;
                case 7:
                    break;
            }
        }
    }
}

Answer 1

在您描述的情况下，一种方法是使用闭包，如下所示:

var id = y + "," + x;
(function(id) {
    document.getElementById(id).onclick = function() {
        console.log(id);
    };
})(id);

但是，使用 addEventListener 总是更容易(对于 IE 则为 AttachEvent):

document.getElementById(y+","+x).addEventListener("click", function() {
    console.log(this.id);
}, false);