Remove an object in an array of arrays in JavaScript or Typescript

Question

I am trying to delete/remove an object which is at at position x in array A such that Array A is inside another array such as this:

    var lol = [ 
            [
              {'a':1},
              {'b':2},
              {'c':3}
            ], 
            [
              {'d':4},
              {'e':5},
              {'f':6}
            ], 
            [
              {'g':7},
              {'h':8},
              {'i':9}
            ]
];

Now lets say I would like to remove object with key 'f'. I have a

function deleteNestedElement(outerIndex, innerIndex) {
        lol[outerIndex].splice(0, innerIndex);
}

on calling

deleteNestedElement(2,0);
alert(lol);

I am getting the result as this:

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Here is my JsFiddle

I need to delete the specific element as desired from this array.

you get the same type of output if you alert(lol) before your function call. you're alerting objects, not strings, so that's what your output is going to be. Try doing a console.log instead, or using the browser debugging tools. — BlackICE, Dec 20 '18 at 13:50
You need to read up on how `splice()` works. Also using `alert()` is a useless debugging tool for arrays of objects — charlietfl, Dec 20 '18 at 13:50
@charlietfl, thanks, I was wondering if splice is doing something to array that is why it is like this in alert. I get it now. — Muhammad Ahsan, Dec 20 '18 at 14:03
How would you know when you can't see what's in each object? Logging to console lets you see changes — charlietfl, Dec 20 '18 at 14:04

Ori Drori · Accepted Answer · 2018-12-20T14:00:24.370

To remove items Array.splice() expects an index (1st param), and the number of items you wish to remove (2nd param). You passed 0 and 0 - remove 0 items from index 0, so nothing was removed.

In addition alert() converts JS objects to strings, and this is what you see. Use console.log() instead.

function deleteNestedElement(outerIndex, innerIndex) {
  lol[outerIndex].splice(innerIndex, 1);
}

var lol = [[{"a":1},{"b":2},{"c":3}],[{"d":4},{"e":5},{"f":6}],[{"g":7},{"h":8},{"i":9}]];

deleteNestedElement(1, 2); // this will remove the "f" object
deleteNestedElement(2, 0); // this will remove the "g" object
console.log(lol);

score 2 · Answer 2 · answered Dec 20 '18 at 13:51

Array.splice function takes first parameter as index and second parameter as number of elements to be deleted. In our case it should be splice(innerIndex, 1) as we need to delete 1 element at a particular index i.e. innerIndex.

Also, index of array start from 0, hence for 2nd item in array, you will need to pass 1 for outerIndex and similarly 2 for innerIndex like deleteNestedElement(1,2)

var lol = [[{"a":1},{"b":2},{"c":3}],[{"d":4},{"e":5},{"f":6}],[{"g":7},{"h":8},{"i":9}]];

function deleteNestedElement(outerIndex, innerIndex) {
        lol[outerIndex].splice(innerIndex, 1);
}

deleteNestedElement(1,2);
console.log(lol);

Remove an object in an array of arrays in JavaScript or Typescript

2 Answers2