How to read names of arrays within an array?

[Squarepusher]

Hello,

I'm currently learning JavaScript and I plan to work a lot with arrays. I store all arrays in external files and use JSON to access them. Now I wanted to read the names of all arrays that are nested in one main array to create a navigation list but I don't know how to do that.

 

This is an example of a JSON file I use:

{"MainArray":[
  {"SubArray1":[{
     ...
  }]
  },
  {"SubArray2":[{
     ...
  }]
  },
  {"SubArray3":[{
     ...
  }]
  }
]}

How do I get the names of all SubArrays? I tried this

// arr is a JSON-parsed string
function myFunction(arr) {
  var out = "";
  var i;
  for(i = 0; i < arr.MainArray.length; i++) {
    out += arr.MainArray[i].toString() + '<br>';
  }
  document.getElementById("aso").innerHTML = out;
}

but it only creates a list of "[object Object]" items. Should I create another JSON file where all array names are listed instead?

[Ingolme]

You need a better way to structure your data. Something like this, for example:

{
  name : "MainArray",
  data : [
    {
      name : "SubArray1",
      data : [
        ...
      ]
    },
    {
      name : "SubArray2",
      data : [
        ...
      ]
    },
    {
      name : "SubArray3",
      data : [
        ...
      ]
    }
  ]
}

[davej]

I'm currently learning JavaScript and I plan to work a lot with arrays. I store all arrays in external files and use JSON to access them. Now I wanted to read the names of all arrays that are nested in one main array to create a navigation list but I don't know how to do that.

 

You don't explain why you have this type of data-structure.

[Squarepusher]

 

You need a better way to structure your data. Something like this, for example:

{
  name : "MainArray",
  data : [
    {
      name : "SubArray1",
      data : [
        ...
      ]
    },
    {
      name : "SubArray2",
      data : [
        ...
      ]
    },
    {
      name : "SubArray3",
      data : [
        ...
      ]
    }
  ]
}

 

I don't know how to access these array...

 

 

You don't explain why you have this type of data-structure.

 

I want to change content on the page without loading a whole new page. Just like AJAX.

[justsomeguy]

Those are objects and arrays. If that structure is stored in a variable called obj, then you can loop through it like this:

 

var name1 = obj.name;
for (var i = 0; i < obj.data.length; i++) {
  var name2 = obj.data[i].name;
  for (var j = 0; j < obj.data[i].data.length; j++) {
    ...
  }
}

If you're going to be using that kind of thing you'll want to look into objects and arrays in Javascript. JSON is just a shorthand notation to create them, you're creating objects and arrays though. You'll need to be familiar with them regardless of the actual structure you eventually use. Objects make it easier because you can name the properties. Those objects have a property called name that is a string and another property called data that is an array.