Develop Reference

Looping through items in an array of objects

I have an array of objects.
ABC.getAggregation("V")[0].getItems();
this produces the result:
MY ARRAY OF OBJECTS
In the console i can get the result i am looking for by specifying the position of the item like this:
ABC.getAggregation("V")[0].getItems()[0].getPosition()
ABC.getAggregation("V")[0].getItems()[1].getPosition()
ABC.getAggregation("V")[0].getItems()[2].getPosition()
The result of the above code produces string values e.g "3.4554,43,0".
How can i loop through each item and get the position in my code. just like the above code that i typed in the console. there wont always be 3 objects this is why i cant hard code the above 3 lines.

Try using a the Array.prototype.forEach() function. The function will be called for each element in the array, passing in the element as the first parameter.
ABC.getAggregation("V")[0].getItems().forEach( function (item) {
item.getPosition();
//do something else
});
More on ".forEach()"
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

You can treat it like any other array:
var myArray = ABC.getAggregation("V")[0].getItems();
for(var i=0; i< myArray.length; i++){
myArray[i].getPosition(); //Do something with the position.
}

You can use for loop to iterate trough all of them.
for(var i=0; i<ABC.getAggregation("V").getItems().length; i++) {
ABC.getAggregation("V")[0].getItems()[i].getPosition();
}

You can use forEach loop to iterate trough all of them.
ABC.getAggregation("V").getItems().forEach (item, index) {
return ABC.getAggregation("V")[0].getItems()[index].getPosition();
}

A very simple way to iterate through each object in the array is just with a for loop on the array, you don't even need to declare your iterating variable.
ex:
var anArray = ['one', 'two', 'three'];
for( i in anArray){
console.log('index #: ' + i );
console.log(anArray[i]);
}
will print out all the elements in anArray:
index #: 0
one
index #: 1
two
index #: 2
three

!! Apparently this is a good example of how not to do it :P
You can assign the items to an array and loop through them like this:
var items = ABC.getAggregation("V")[0].getItems();
var returnString = "";
for (var key in items ) {
if (items .hasOwnProperty(key)) {
var element = items [key];
returnString += element.getPosition() + ',';
}
}
returnString = returnString.substring(0, x.length-1);
console.log(returnString);

Looping over associative array

I'm adding a bunch of input fields into an associative array. I can access the individual elements fine, eg. this works:
arr = new Array();
field = document.getElementById("someField");
arr[field] = someValue;
alert(arr[field].id);
But when I try to loop over them, the id shows up as undefined, and only one element is looped over.
for (var elem in arr) {
alert(elem.id + " " + arr[elem]);
}
Am I looping over it wrong?
Edit: arr.length shows up as 0 for some reason even though I'm able to access its elements.

the key in a javascript-array has to be a number or string.
field is automatically converted to a string with toString().
arr = new Array();
field = document.getElementById("someField");
var key = field.toString();
arr[key] = someValue;
alert(arr[key].id);
in your for-loop, you iterate the keys of that array.
field.toString() in that case.
and a string does not have a id-property.
this will work:
for (var elem in arr) {
alert(arr[elem].id + " " + arr[elem]);
}
by the way toString() of a DOM-Element ist often a generic string like "[SpanElement]".
if you try to add multiple span-elements, you're effectivle overriding the item with "[SpanElement]" as key and end up with just one element.
in respect to #user2736012 comments, i encourage everyone to read
"JavaScript Associative Arrays Demystified"

Any associative array in JavaScript is an object. Arrays are objects that have special methods because they are numerically indexed. So your code should look something like this:
obj = {};
field = document.getElementById("someField");
obj[field] = someValue;
for (var p in obj) {
alert(obj[p].id);
}

how to generate arrays automatically in javascript?

I want to make a loop that makes arrays automatically and assign the values to it.
The problem is how to generate the array itself automatically.
for(var attGetter=1; attGetter <= num; attGetter++){
var catesArray1 = new Array();
for(var atttGetterArray=1; atttGetterArray <= series; attGetterArray++){
idOfInput = "cate"+chartGetter+"_series"+attGetterArray;
catesArray1.push($("#"+idOfInput).val());
}
}
I want the loop to generate the array itself automatically like
catesArray1
catesArray2
catesArray3
and so on..

You need an object or an array to hold the multiple arrays you wish to create. Maybe something you are looking for is like the following?
var arrayHolder = new Array();
for(var attGetter=1; attGetter <= num; attGetter++){
var catesArray = new Array();
for(var attGetterArray=1; atttGetterArray <= series; attGetterArray++){
idOfInput = "cate"+chartGetter+"_series"+attGetterArray;
catesArray.push($("#"+idOfInput).val());
}
arrayHolder.push(catesArray);
}

If you want the arrays to be in global namespace, You can try
window['catesArray' + attGetter] = [];
...
window['catesArray' + attGetter].push(...)
Else you can create a hash object and use it to hold the reference
var obj = {};
.....
obj['catesArray' + attGetter] = [];
.....
obj['catesArray' + attGetter].push(...)

In that case you will have to create one new array that holds all the cacatesArrays from first for loop
var catesArrayContainer = new Array(); //<<<---------------------
for(var attGetter=1; attGetter <= num; attGetter++){
var catesArray = new Array();
for(var atttGetterArray=1; atttGetterArray <= series; attGetterArray++){
idOfInput = "cate"+chartGetter+"_series"+attGetterArray;
catesArray.push($("#"+idOfInput).val());
}
catesArrayContainer.push(catesArray); //<<<--------------------
}
EDIT :
This happens because the scope of variable catesArray1 was limited. When the loop enters next iteration the catesArray1 gets reinitialized, thus losing all the previously stored values...
Now in the code I have posted, we are storing every instance of catesArray1 in another array, and your values persist out side of the for loop

You can do something like this for 4 arrays of 5 elements each
yourarray=[];
for (i = 0; i <4; i++) {
temparray=[];
for (j = 0; j < 5; j++) {
temparray.push($('#'+whateverID+'_'+i+'_'+j)) //your values here
}
yourarray.push(temparray);
}
Check it on this JSFiddle. open chrome console to see array
If you want to create array within loop from index
You can use eval to evaluate javascript from strings but i wont use that unless there is no other way. you can see both above and eval method in this Fiddle. Open Chrome console to see array values
Just a comparison of using eval and 2D array
Open console in chrome while you run this jsFiddle and you will see the difference in eval and 2darray in context of this question.

You should assign them to an object. In this case, make an object variable before the first for-loop to hold all arrays:
var allArrays = {};
for(var attGetter=1; attGetter <= num; attGetter++){
var currentArray = allArrays['catesArray' + attGetter] = new Array();
for(var atttGetterArray=1; atttGetterArray <= series; attGetterArray++){
idOfInput = "cate"+chartGetter+"_series"+attGetterArray;
currentArray.push($("#"+idOfInput).val());
}
}

Instead of attempting to create & allocate dynamically named variables, I would think of this more of an array of array's if you will. In other words, create an array that holds all of the arrays you want:
var collections = []; // Literal notation for creating an array in JS
From here, it's a matter of making each value you create within this array its own array:
var n = 10; // Total amount of arrays you want
for (var i = 0; i < n; i++) {
var values = [];
// Have another loop that fills in the values array as expected
collections.push(values); // Each element at collections[i] is its own array.
}
If you truly need named elements, you could potentially do something very similar with just an object {} instead, and refer to each element by a name you create.
var collections = {}; // Literal notation for an object in JS
var n = 10; // Total amount of arrays you want
for (var i = 0; i < n; i++) {
var values = []; // Literal notation for an array in JS
// Fill in the values array as desired
var name = 'arr' + i; // How you'll refer to it in the object
collections[name] = values;
}
I suggest the former though, since it does not sound like you need to have explicit names on your arrays, but just want multiple layers of arrays.

concat empty / single item array

Ok, so I have this simple code :
for(var i=0; i<lines.length; i++) {
elements += myFunction(lines[i]);
}
Where elements is an empty array at the start and myFunction() is just a function that returns an array of strings.
The problem is that if myFunction() returns an array with a single string, the += is interpreted as a string concat in place of an array concat.
At the end of the loop the result is just a long string and not an array.
I tried push()ing the values in place of concatenation, but this just gives me a two dimensional matrix with single item arrays.
How can I solve this typecasting problem ? Thank you in advance !

Try :
for(var i=0; i<lines.length; i++) {
elements [i] = myFunction(lines[i]);
}
I suppose it solves the problem.

You can use the Array concat function:
elements = elements.concat(myFunction(lines[i]));

Presumably you want something like:
var arrs = [[0],[1,2],[3,4,5],[6]];
var result = [];
for (var i=0, iLen=arrs.length; i<iLen; i++) {
result = result.concat(arrs[i]);
}
alert(result); // 0,1,2,3,4,5,6
Ah, you want to concatenate the results of a function. Same concept, see other answers.

You can also use myArray[myArray.length] = someValue;

let newArray = [].concat(singleElementOrArray)

Javascript for loop var "i" is treated as a string?

I am using Titanium to build some mobile apps and I noticed that this will give a result that I wasn't expecting.
data = ['a','b', 'c','d'];
for (var i in data){
Ti.API.debug(i+1);
};
This will print: 01,11,12,13
Is this something particular to Titanium or is it generally in Javascript?
Why isn't 'i' being treated as an integer? I am very confused.
Thanks for your help.

This doesn't directly answer your question, but if you are looping through an array you should not use for (var i in data). This loops through all members of an object, including methods, properties, etc.
What you want to do is this:
for (var i=0, item; i<data.length; i++) {
item = data[i];
}

data is an array, so you use a for loop, not a for-in loop:
var data = [ ... ];
var i;
for ( i = 0; i < data.length; i += 1 ) {
Ti.API.debug( i + 1 );
}
Alternatively, you can use the forEach array method:
data.forEach( function ( val, i ) {
Ti.API.debug( i + 1 );
});

The reason why you see this behavior is that the type of i when using a for-in over an array is string not int. Hence the + is doing string concatenation and not addition. If you want it to be the numerical value then use a for loop
for (var i = 0; i < data.length; i++) {
Ti.API.debug(i + 1);
}

Try this:
data = ['a','b', 'c','d'];
for (var i in data){
Ti.API.debug(i*1+1);
};
Multiplying i x 1 will force it to recognize it as numeric.

Try this:
Ti.API.debug(parseInt(i)+1);

You can do
data = ['a','b', 'c','d'];
for (var i in data){
console.log(parseInt(i)+1);
};
But it is not recommended. Because in Javascript for..in loop is for key:value pairs (Objects). So if use it with an array each index is converted to string as key.
so always use for(i = 0; i < length; i++) with arrays.

This is because javascript handles for-each loop this way.
In other languages for(i in datas) will loop through each data.
But in javascript the i will have index value instead of data. so you have to get data by datas[i].