Delete from array in javascript

Question

3 hours ago, I asked a question in SO , about deleting a part of an object, so I linked this question to it:

delete a part of object in javascript

but now another problem occurred when I deleted from that array. I use that object to populate a FlexiGrid. but when I delete an item from that object by following code, instead of delete that item , it sets to undefined :( and flexigrid did not accept it for input data.

for (var i = 0; i < Roomdata.length; i++) {
 if(Roomdata[i].id = X) {
 delete Roomdata[i];
 break;
 }
} 

For example, imagine I have 3 items in Roomdata like this :

{item1, item2, item3}

When I call this code to delete item2 , Roomdata object looks like this :

{item1, undefined, item3}

and this is a bad format to be accepted by flexigrid as input data

Is there any solution ?

Thanks every body and sorry about my bad syntax (I am new in English)

regards , Foroughi

• Felix Kling: possible duplicate of JavaScript Array Delete Elements -- please use the search before you ask a question.
• Felix Kling: The accepted answer to your previous question already suggest to use splice. Why do you ask this question again?
• Ali Foroughi: Sorry @Felix , but I think because I asked a question about this issue already , I asked this question to help readers to read more understandable question ,anyway sorry about that
• Ali Foroughi: @FelixKling , because i use that reply , but it not work , but i use his idea to solve my problem, so i accepted it not because his answer is correct , because his answer give me an idea
• Felix Kling: @Rob: The duplicate answer shows how to delete an element form an array which was the question. I don't think we have to spoon feed every solution in detail. See also my comment to your answer.

Answer 1

Walk through the array in reverse order, and use .splice to remove the element.
You have to walk in the reverse order, because otherwise you end up skipping elements ^{See below}.

for (var i = Roomdata.length-1; i >= 0; i--) {
 if (Roomdata[i].id == X) {
 Roomdata.splice(i, 1);
 break;
 }
}

What happens if you don't walk in the reverse order:

// This happens in a for(;;) loop:
// Variable init:
var array = [1, 2, 3];
var i = 0;
array.splice(i, 1); // array = [2, 3] array.length = 2
// i < 2, so continue
i++; // i = 1 
array.splice(i, 1); // i=1, so removes item at place 1: array = [2]
// i < 1 is false, so stop.
// array = [2]. You have skipped one element.

• Ali Foroughi: thank you for complete reply and its comments, anyway you help me and you are great,thanks again
• Felix Kling: You don't have to traverse the element in reverse order as you are terminating the loop after you call splice anyway. If you want to remove multiple elements from an array, then yes, but in this case it is not needed.
• Rob W: @FelixKling You're right. However, since the accepted answer at the other question didn't work, I assume that break; have to be removed.
• Ali Foroughi: @RobW , yes , it is because I want to remove just one item and the breke the loop, i can traverse it normaly :)
• Eric Smith: Should that be if (Roomdata[i].id === X) { instead (equality vs. assignment)?

Answer 2

What you have is an Array. You should use the splice() method to remove an element from an array, not by deleteing the element.

for (var i = 0; i < Roomdata.length; i++) {
 if(Roomdata[i].id = X) {
 Roomdata.splice(i, 1);
 break;
 }
} 

• Rob W: The second argument specifies how many items have to be removed. .splice(i,0) doesn't remove anything. Even if you replace it with .splice(i,1), you're skipping elements by not accounting for the changed index.
• Matt: @RobW: Whoops. And as for skipping elements, he's breaking on removal anyway, so nothings going to get skipped.

Answer 3

Using splice in spite of delete.

 Roomdata.splice(i, 0);

splice attribute removes blank string elements, undefined references, NULLs and FALSEs.

it will solve your problem

Answer 4

To remove all of the elements of an array matching a particular value, you can do this:

// Remove all elements in arr[] matching val
for (let i = 0; i < arr.length; i++) {
 if (arr[i] === val) {
 arr.splice(i--, 1); // Remove arr[i] and adjust the loop index
 }
}

Note that this is a forward scan of the array. The decrement of the loop index is necessary so that the loop does not skip the next element after an element is removed.