數組中的 javascript 函數 arguments

Question

我想做的是這個

    $.each($(".canvas"), function(n) {
        var canvas = $(this)[0].getContext("2d");     
        canvas.drawImage(options[n]);
    });

其中 options 將是 arguments 的數組，但無法弄清楚該數組應如何格式化才能正常工作

明顯不是

['img, 0,  0, 70, 17, 21, 16, 70, 17', 'img, 0,  0, 80, 12, 21, 16, 70, 17']

這既不是

[''+img+', 0,  0, 70, 17, 21, 16, 70, 17', ''+img+', 0,  0, 80, 12, 21, 16, 70, 17']

也不是這個

{0: [img, 0,  0, 70, 17, 21, 16, 70, 17]}

這也行不通

var options = [[img, 0,  0, 70, 17, 21, 16, 70, 17],
               [img, 0, 16, 70, 17, 21, 16, 70, 17],
               [img, 0, 32, 70, 17, 21, 16, 70, 17],
               [img, 0, 48, 70, 17, 21, 16, 70, 17]];

img.onload = function() {
    $.each($(".canvas"), function(n) {
        var canvas = $(this)[0].getContext("2d");     
        canvas.drawImage(options[n].join(', '));
    });
};

錯誤總是 Uncaught TypeError: Type error 或 Uncaught TypeError: Illegal invocation

Answer 1

使用Function.apply 。

canvas.drawImage.apply(canvas, options[n]);

options[n]看起來像

[img, 0, 0, 70, 17, 21, 16, 70, 17]

---

完整示例：

var options = [[img, 0,  0, 70, 17, 21, 16, 70, 17],
               [img, 0, 16, 70, 17, 21, 16, 70, 17],
               [img, 0, 32, 70, 17, 21, 16, 70, 17],
               [img, 0, 48, 70, 17, 21, 16, 70, 17]];

$(img).load(function()
{
    $(".canvas").each(function(n)
    {
        var canvas = this.getContext('2d');     
        canvas.drawImage.apply(canvas, options[n]);
    });
});

演示： http://jsfiddle.net/mattball/5EQbC/