如何将字符串数组作为 arguments 传递给 function？

Question

I have a couple of arrays, like so:

var galImgs = ["http://domain.tld/gallery/image-001.jpg",
               "http://domain.tld/gallery/image-002.jpg",
               "http://domain.tld/gallery/image-003.jpg"],
    preloadImgs = [];

And I'd like to use a simple for loop to load images from the values in the galImgs array, like so:

function preload() {
    for (i = 0; i < preload.arguments.length; i++) {
    preloadImgs[i] = new Image();
    preloadImgs[i].src = preload.arguments[i];
    }
}

However, calling

preload(galImgs);

passes in the array as a single string, instead of comma-separated strings. How can I pass the galImgs array so it will be read as individual arguments?

Answer 1

However, calling

preload(galImgs);

passes in the array as a single string, instead of comma-separated strings.

No, it passes in the array, not a string. You've actually gone to too much trouble in your preload function, just use the array you were given:

function preload(a) {
    for (i = 0; i < a.length; i++) {
        preloadImgs[i] = new Image();
        preloadImgs[i].src = a[i];
    }
}

(And declare the i variable within the function, which I haven't added above; as it is, you're falling prey to The Horror of Implicit Globals .)

This has the advantage of not using the arguments pseudo-array, which is a performance hit on most implementations.

If you want, though, you can use an array to pass discrete arguments to preload , via the apply function:

preload.apply(undefined, galImgs);

The first argument is used for this within the function, you can just use undefined for the default; the second argument is the array, which will show up in the function as discrete arguments.

Answer 2

The problem is your using the arguments keyword to find the passed in event. What you really want is

function preload(images) {
    for (i = 0; i < images.length; i++) {
    preloadImgs[i] = new Image();
    preloadImgs[i].src = images[i];
    }
}

To help you understand better, your old way was fine except one thing..

preload.arguments.length == 1
preload.arguments[0] == galImgs
preload.arguments[0][0] == galImgs[0]

Answer 3

You are looking for the apply method:

preload.apply(null, galImgs);

Should do it!

Answer 4

There's nothing to worry about having viewing it as a single string. Just by providing index to your array, you would be able to get the individual strings.

galImgs[0] would return you the string "http://domain.tld/gallery/image-001.jpg"

You can use gallmgs is an array object and you would have all the accessors of an array in this. Try gallmgs.length.