数组中的 JavaScript 函数参数

Question

我想做的是这个

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

其中选项将是一个参数数组，但无法弄清楚应该如何格式化该数组才能使其工作

显然不是

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

这两者都不是

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

也不是这个

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

这也行不通

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(', '));
    });
};

错误始终为“Uncaught TypeError: Type error”或“Uncaught TypeError: Illegal invocation”

Answer 1

使用Function.apply .

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

其中选项[n]看起来像

[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/