Is it possible to create an empty multidimensional array in javascript/jquery?

问题

I am trying to create a very basic Flickr gallery using the Flickr API. What I want to achieve is sorting my pictures by tag. What I am using is jQuery.getJSON() so that I can parse the API response of flickr.photosets.getPhotos.

The data I am interested in getting from Flickr is the tag and the URL associated to each photo. The problem with this is that the only logical way out of this for me is creating a multidimensional array of the following format:

Array['tag1'] => ['URL_1', 'URL_2', 'URL_3', 'URL_n'];

However, I cannot find any way to achieve this. My code looks like this:

$.getJSON('http://api.flickr.com/services/rest/?api_key=xxx&method=flickr.photosets.getPhotos&user_id=xxx&format=json&extras=tags%2C+url_l%2C+url_sq&nojsoncallback=1&photoset_id=xxx', 
   function(data) {

     var imageArray = [];   
     $.each(data.photoset.photo, function(i, item) {

       imageArray[item.tags] = [item.url_sq,];

     });
});

I am aware that the code might look awkward, but I've tried everything and there's no way I can figure this out.

回答1:

var arr = [];
arr[0] = [];
arr[0][0] = [];
arr[0][0][0] = "3 dimentional array"

Multi dimentional arrays have a lot of gaps unless they are used properly. A two dimensional array is called a matrix.

I believe your data contains a space seperate string called "tags" containing the tags and a single url.

var tagObject = {};
data.photoset.photo.forEach(function(val) {
  val.tags.split(" ").forEach(function(tag) {
    if (!tagObject[tag]) {
      tagObject[tag] = [];
    }
    tagObject[tag].push(val.url_sq);
  });
});
console.log(tagObject); 
/*
  {
    "sea": ["url1", "url2", ...],
    "things": ["url4", ...],
    ...
  }
*/

I don't know how it returns multiple tags.

回答2:

I think the syntax you are attempting to achieve is something like the following:

var item = {"tags":"blah","url_sq":"example.com"}; // for sake of example.
var imageArray = [];
$.each(data.photoset.photo, function(i, item) {
   imageArray.push({"tags":item.tags,"url":item.url_sq});
});

and then reference it like this:

imageArray[0].tags
imageArray[0].url
imageArray[1].tags
imageArray[1].url
...

回答3:

JavaScript doesn't have true multidimensional arrays (heck, it doesn't even have true regular arrays...), but, like most languages, it instead uses arrays of arrays. However, to me it looks like you need an object (kinda similar to PHP's arrays) containing arrays.

var data = {
    tag1: ['URL_1', 'URL_2', 'URL_3', 'URL_n']
};
// Then accessed like:
data.tag1; // ['URL_1', ...]
data.tag1[0]; // 'URL_1'
data.tag1[1]; // 'URL_2'
// etc.

So, you're problem would look something like this:

var tags = {};
$.each(data.photoset.photo, function (i, item) {
    $.each(item.tags.split(" "), function (i, tag) {
        if (!tags[tag])
            tags[tag] = [];
        tags[tag].push(item.url_sq);
    });
});
// tags is now something like:
// {
    "foo": ["/url.html", "/other-url/", ...],
    "bar": ["/yes-im-a-lisp-programmer-and-thats-why-i-hypenate-things-that-others-might-underscore-or-camelcase/", ...],
    ...
//}

回答4:

Maybe something like that in your each:

if ( imageArray[item.tags] != null ){
   imageArray[item.tags][imageArray[item.tags].length] = item.url_sq;
}else{
   imageArray[item.tags] = [];
}

回答5:

Yes it is! I found this to be quite fast. I might stretch to say that it could be the fastest way possible to generate a N Dimensional array of Ns lengths resulting in empty arrays using JavaScript. (i.e. an arbitrary number of dimensions each with an arbitrary length)

Even though the definition of an array in JavaScript is foggy at best.

function createNDimArray(dimensions) {
    var t, i = 0, s = dimensions[0], arr = new Array(s);
    if ( dimensions.length < 3 ) for ( t = dimensions[1] ; i < s ; ) arr[i++] = new Array(t);
    else for ( t = dimensions.slice(1) ; i < s ; ) arr[i++] = createNDimArray(t);
    return arr;
}

Usages:

var arr = createNDimArray([3, 2, 3]); 
//  arr = [[[,,],[,,]],[[,,],[,,]],[[,,],[,,]]]
console.log(arr[2][1]); // in FF: Array [ <3 empty slots> ]
console.log("Falsy = " + (arr[2][1][0]?true:false) ); // Falsy = false

If you care to read more; check my answer to this question.

回答6:

I think something like this should do what you want

 var imageArray = [];   

 $.each(data.photoset.photo, function(i, item) {

   // if the tag is new, then create an array
   if(!imageArray[item.tags])
     imageArray[item.tags] = [];

   // push the item url onto the tag
   imageArray[item.tags].push(item.url_sq);

 });