I don't understand the point of having the second parameter in the splice method.
var example = [ 'one', 'two', 'three' ]
example.splice(0,1)
Looking at articles and it says the second parameter determines how many item get removed. But it seems to me that there is always only one item in a single position.
What is the point of indicating how many items you want to delete when there will only be one item in a single position?Can you have multiple items in a single indice/index?
array.splice(start, deleteCount)
The documentation says that the second paramter determines how many elements you want to delete. So you might use it to delete 2 or more entries from an array with this at a specific position.
Related
a = ['a','b','c','d','e'];
console.log(a.splice(1));
console.log(a);
In splice documentation, it says that skipping the delete parameter will delete all array items, yet here they're not; the first one is left out. Why is this?
Edit: My expectations was that haveing the omission of the delete parameter would cause to delete all the items of the array. But now after read Baconnier comment I understand that removes all after the index (first parameter).
then all the elements from start to the end of the array will be deleted. start being 1 in your case.
a = ['a','b','c','d','e'];
console.log(a.splice(0));
console.log(a);
Arrays start at 0, if you want to delete all elements including the first one you need to pass 0 as the first parameter.
This is the JSON stored in my chrome local storage
{"users":[
{"password":"123","userName":"alex"},
{"password":"234","userName":"dena"},
{"password":"343","userName":"jovit"}
]}
Is it possible to remove a specific item in "users" ?
I tried to this code but no luck
chrome.storage.local.remove('users[0]', function(){
alert('Item deleted!');
});
There is no magic syntax to delete only one element from an array that is stored in chrome.storage. In order to delete an item from the array, you has to retrieve the stored array, throw away the unwanted items (or equivalently, keep only the items that you want to keep), then save the array again:
chrome.storage.local.get({users: []}, function(items) {
// Remove one item at index 0
items.users.splice(0, 1);
chrome.storage.set(items, function() {
alert('Item deleted!');
});
});
See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice.
Note that if you want to delete one or more items whose value satisfies a certain condition, you have to walk the array in reverse order. Otherwise you may end up removing the wrong items since the indices of the later elements are off by one after removing the first item, off by two when you've removed two items, etc.
Yes you can try this
chrome.storage.sync.remove("token");
see documentation
I try to remove the first Item so that all other move up in an Array I create with
..
Queue: [],
..
and dynamically push Items into.
I later use slice to remove them and have then next Item be the first one.
..
thread.Queue.slice(0, 1);
..
It should return the first Item of the Array, which it does, but it should also remove it from the array and move all other up.
Here is a example which shows, that is neither working in the Browser. (I found this 'behaviour' in Node.js)
http://jsfiddle.net/bTrsE/
or rather
http://gyazo.com/b3dcdbf4f74642c04fe1c1025f225a08.png
Array.Slice = Is an implementation of SubArray, From an array you want to extract certain elements from the index and return a new array.
Example:
var cars = ['Nissan','Honda','Toyota'];
var bestCars = cars.splice(0,1);
console.log(bestCars);
//This should output Nissan Because i like Nissan
For your problem you should be looking Array.Splice(), splice adds / removes an element from the index
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
The .slice() method does not alter the original array. It returns a shallow copy of the portion of the array you asked for.
I need help with a loop... it's probably simple but I'm having difficulty coding it up.
Basically, I need to check existing Ids for their number so I can create a unique id with a different number. They're named like this: id="poly'+i'" in sequence with my function where i is equal to the number of existing elements. Example: Array 1, Array 2, Array 3 corresponding with i=1 for the creation of Array 1, i=2 for Array 2, etc.
Right now i is based on the total number of existing elements, and my "CreateNew" function is driven off x=i+1 (so the example above, the new element will be named Array 4). The problem is that if you delete one of the middle numbers, the "Create" function will duplicate the high number. i.e. Array 1, 2, 3 delete 2, create new-> Array 1, 3, 3.
I need an if() statement to check if the array already exists then a for() loop to cycle through all i's until it validates. Not sure how to code this up.
The code I'm trying to correct is below (note I did not write this originally, I'm simply trying to correct it with my minimal JS skills):
function NewPanel() {
var i = numberOfPanels.toString();
var x = (parseInt(i)+1).toString();
$('#items').append('<div onclick="polygonNameSelected(event)" class="polygonName" id="poly'+i+'"> Array '+ x +' </div>');
$('div[id*=poly]').removeClass('selected');
$('#poly'+i).addClass('selected');
$('#poly'+i).click(function() {
selectedPolygon = i;
$('div[id*=poly]').removeClass('selected');
$(this).addClass('selected');
});
}
THANK YOU! :)
Please clarify "The problem is that if you delete one of the middle numbers, ". What do you mean by delete? Anyway, the simplest solution is to create two arrays. Both arrays will have the same created id's. Whenever an id is created in the first array, an id will be added to the second array. So when it is deleted from first array, check your second array's highest value and then create this id in first array. I hope this did not confuse you.
Well it is hard to tell why you cannot just splice the array down. It seems to me there is a lot of extra logic involved in the tracking of element numbers. In other words, aside from the index being the same, the ids become the same as well as other attributes due to the overlapping 1, 3, 3 (from the example). If this is not the case then my assumption is incorrect.
Based on that assumption, when I encounter a situation where I want to ensure that the index created will always be an appending one, I usually take the same approach as I would with a database primary key. I set up a field:
var primaryKeyAutoInc = 0;
And every time I "create" or add an element to the data store (in this case an array) I copy the current value of the key as it's index and then increment the primaryKeyAutoInc value. This allows for the guaranteed unique indexing which I am assuming you are going for. Moreover, not only will deletes not affect future data creation, the saved key index can be used as an accessor.
rowData = [];
alert(rowData[0]);
gives me [Ti.UI.TableViewRow]
Now how can i remove this element... i have been using rowData.splice(), but i have no idea on what to pass to remove it.
Thanks
try rowData.splice(0, 1); the first argument indicates the index of item to be removed, the second indicates how many items should be removed
In the code you present rowData should be empty, so rowData[0] should be undefined. I suppose something is pushed to rowData in between? Anyway, there are several ways to remove elements from arrays:
You can remove all elements at once
from an array using rowData.length =
0.
If you want to remove 1 element, use
the Array.splice method. E.g.
removing the first element:
rowData.splice(0,1) (means remove
1 element of rowData starting from
element 0 (the first element).
If it's only the first element you
want to remove you could also use the
shift method: rowData.shift().
The last method you can use is
slice: rowData = rowData.slice(1)
(means: give me all elements from
rowData starting at the first element and
assign the result to rowData),
or rowData.slice(1,4) (means:
give me all elements from
rowData starting at the first element,
ending at the fourth element, and
assign the result to rowData).
If you want to remove the element(s) entirely, splice() will return a new array with the member(s) removed.
You can also use the delete operator, but this won't affect the Array size and the member will be undefined. This is will also make it non enumerable.