I have a decoded Json variable called objIntChart that looks like the following when I console.log() it.
The problem is I need it as an array that looks like this
I did a foreach loop like this in an attempt to solve it:
var array = [];
objIntChart.forEach(function (entry) {
var x = 0++;
array.push(x);
array.x.push(entry['dateTime']);
array.x.push(entry['entries']);
});
However the problem is that I cannot do a push on array.x because it takes the x as the name and not the variable. Is there a solution to this?
Keep it simple:
var array = [];
objIntChart.forEach(function (entry) {
array.push([entry['dateTime'], entry['entries']]);
});
This will do as well:
var arr = objIntChart.map(function (obj) { return [obj.dateTimes, obj.entries]});
console.log(arr);
You should use array[x] instead of array.x and also be doing array[x] = [] or array.push([]) instead of array.push(x) which will add the integer x, not an empty array, to your array.
Also, you will need to set var x = 0; outside your forloop and do x++ inside it. Currently, x will always be 1 when you use it.
Related
Trying to change my for loop with .map method of jquery.
But I am not getting the output which I use to get in for-loop.
This is my actual loop that get the perfect data in the form of array.
var yourArray = [];
for (var i = 0; i < marray.length; i++) {
mId = marray[i].id;
yourArray.push(mId);
}
same thing I tried using .map()
idArr = marray.map(function(row) {
return row[i].id;
});
But the actual array output is not coming.
It should be :
idArr = marray.map(function(row) {
return row.id;
});
row is the current value, not the entire array. So no need for the i.
Fiddle
Array.prototype.map()
Try using $.map() from jquery,
idArr = $.map(marray, function(v,i) {
return v.id;
});
I want to find out how many items are in my JSON object. I have seen many answers but they all deal with a common value to loop through. I am wanting the results to tell me that there are 2 items in this object. Any help would be great!
[{"manager_first_name":"jim","manager_last_name":"gaffigan"}]
You could use Object.keys in newer browsers. It would return an array of all the keys in the object, and that array would have a length property that will tell you how many items there are in the object :
var arr = [{"manager_first_name":"jim","manager_last_name":"gaffigan"}];
var length = Object.keys(arr[0]).length;
FIDDLE
In non-supporting browsers, you have to iterate
var arr = [{"manager_first_name":"jim","manager_last_name":"gaffigan"}];
var i = 0;
for (var key in arr[0]) i++;
FIDDLE
You can do this:
var arr = [{"manager_first_name":"jim","manager_last_name":"gaffigan"}],
length = 0,
obj = arr[0]; // Get first obj from array
for(var k in obj){
if( obj.hasOwnProperty(k) ) {
length++;
}
}
console.log(length); // Shows 2
You should use hasOwnProperty because you can also extend an Object with functions, there could otherwise also be count als keys.
Links:
hasOwnProperty
Try
var jsonArr = [{"manager_first_name":"jim","manager_last_name":"gaffigan"}];
var itemCount = JSON.stringify(jsonArr).split('":"').length - 1;
This is, of course, a rather coarse(and unreliable) way of doing it, but if you just want the item count, this should work like a charm.
I have an array defined as:
var subjectCache = [];
I then have some code to build it up, which is working ok.
However, if I try to reference the array by an index, e.g.:
var x = subjectCache[0];
or
var x = subjectCache[1];
I get undefined.
Also subjectCache.length is always 0 (zero).
if I try to reference it by its key, e.g.:
var x = subjectCache['12345'];
it works.
Is this normal? Shouldn't I be able to reference it by its index whatever?
I'm using Internet Explorer, if it makes a difference (and it probably does :( )
[Edit]
this is the code I'm using to build the array, although I really don't think it is to blame.
It's a callback from a webservice call. This is working fine and the array is being populated.
var subjectCache = [];
var subjectCacheCount = 0;
function refreshSubjectsCallback(data) {
// update subjects
// loop through retrieved subjects and add to cache
for( i=0; i < data.length; i++ )
{
var subject = data[i];
var subjectid = subject.SubjectId;
subjectCache[subjectid] = subject;
subjectCacheCount += 1;
}
}
[/Edit]
You're probably assigning keys manually instead of using subjectCache.push() to add new elements to the array:
var array = [];
array['foo'] = 'bar';
console.log(array.length); // 0
The length attribute isn't going to reflect those changes the way you'd expect:
> var a = [];
undefined
> a[100] = 2; // The previous `100` entries evaluate to `undefined`
2
> a.length;
101
Instead, use an object:
var object = {};
object['foo'] = 'bar';
for (var key in object) {
var value = object[key];
console.log(value);
}
From your symptoms, it sounds like you are trying to treat the array as an associative array.
In Javascript, arrays work like this:
var a = [];
a[1] = 10;
alert(a.length);
Objects work like this:
var o = {};
o.myProp = true;
o["myOtherProp"] = false;
Arrays only work with numeric keys not strings. Strings assign properties to the object, and aren't counted as part of length nor it's numeric indices.
When building the array, make sure you are assigning to a numeric position within the array.
No, it will not work, because you haven't created arrays but objects.
you will have to access it by its key.
var x = subjectCache['12345'];
If this works and subjectCache.length doesn't, I think you are making an object not an array. You are confused.
Somewhere along the road you lost the array, and the variable subjectCache points to a different kind of object.
If it was an array, it can't have the length zero and contain an item that is reachable using subjectCache['12345']. When you access an item in an array it doesn't make any difference if you use a numeric index or a string representing a number.
I am trying to set up an array in jQuery and I then need to do a for loop on it. But it seems that I cant use an associative array for some reason?
var items = new Array();
items['foo'] = 123456;
items['bar'] = 789012;
items['baz'] = 345678;
items['bat'] = 901234;
alert(items.length);
This is just a test, but it return 0?
You can't make associative array in JavaScript like what you want, instead you can use Object.
For example:
var items = {
foo : 123456,
bar : 789012,
baz : 345678,
bat : 901234
}
And to calculate the length you can do:
var getObjectSize = function(obj) {
var len = 0, key;
for (key in obj) {
if (obj.hasOwnProperty(key)) len++;
}
return len;
};
Use: getObjectSize(items); // output: 4
For more see here.
Another one is:
Object.keys(items).length;
But not supported by all browsers.
var items = new Array();
items['foo'] = 123456;
The problem lies in the very first line. You believe that you are adding an item to the array at the index foo, but you are actually adding a property to the items variable with a key foo and value 123456. If you were to type items.foo it would give you back your 123456.
The problem with this approach is that adding a property to an array does not magically increase it's length.
If you want to have non-numeric indexes, you need to use an object instead of an array:
var items = {
foo: 123456,
bar: 789012,
baz: 345678,
bat: 901234
};
Another approach might be to set up two different arrays, which you construct in parallel:
var items = [], items2 = [];
items.push('foo');
items2.push(123456);
// etc.
alert(items2.length);
The efficiency of this approach depends on how you'll use it. If you're only going to loop through the list of items and do something to each of them, this approach may be more efficient. But if you need to use it like an associative array (items['foo']), then you're better off building an object.
The .length property returns the highest numerical index of the array. Thus, in your case, there is no numerical index and it returns 0. Try
items[98] = "something";
items.length will be 98..! Use the .length property with caution, and if you also want to count the non-numerical indici, loop over the Object (an Array is also an Object) and count its ownProperties.
This is a really stupid question, but I'm just drawing a blank here...
What type of variable declaration is this:
var s1 = [1,2,3,4]
Also, How can I construct a variable like this from multiple objects when the amount of those objects is unknown. This is what I came up with, which doesn't work.
var s1 = [];
for(x in data[i].uh) {
s1 += data[i].uh[x];
}
var s1 = [1,2,3,4]
is an array declaration of four integers using "Array Literal Notation"
You don't need a loop to copy the array, simply do this:
var s1 = data.slice(0);
or in your example you might want this:
var s1 = data[i].uh.slice(0);
Read more about copying arrays here: http://my.opera.com/GreyWyvern/blog/show.dml/1725165
"The slice(0) method means, return a
slice of the array from element 0 to
the end. In other words, the entire
array. Voila, a copy of the array."
That is called an Array, which can be declared with new Array() or by using the array literal [] as in your example. You can use the Array.push() method (see docs) to add a new value to it:
var s1 = [];
for(x in data[i].uh) {
s1.push(data[i].uh[x]);
}
This
var s1 = [1,2,3,4]
is an array declaration.
To add an element to an array, use the push method:
var s1 = [];
for(x in data[i].uh) {
s1.push(data[i].uh[x]);
}
s1 is an array, it's a proper Javascript object with functions.
var s1 = [];
is the recommend way to create an array. As opposed to:
var s1 = new Array();
(see: http://www.hunlock.com/blogs/Mastering_Javascript_Arrays)
To add items to an array use s1.push(item) so your code would be:
var s1 = [];
for(x in data[i].uh) {
s1.push(data[i].uh[x]);
}
As a side note, I wouldn't recommend using for-in, at least not without checking hasOwnProperty.
It's declaring a local variable with an Array with 4 members.
If you want to append to an Array, use the push() method.
That is an array. To add to arrays you would use Array.push(). For example:
var s1 = [];
s1.push(1);
s1.push(2);