Deleting array elements in JavaScript - delete vs

Question

What is the difference between using the delete operator on the array element as opposed to using the Array.splice method?

For example:

myArray = ['a', 'b', 'c', 'd'];

delete myArray[1];
//  or
myArray.splice (1, 1);

Why even have the splice method if I can delete array elements like I can with objects?

Answer 1

Easiest way is probably

var myArray = ['a', 'b', 'c', 'd'];
delete myArray[1]; // ['a', undefined, 'c', 'd']. Then use lodash compact method to remove false, null, 0, "", undefined and NaN
myArray = _.compact(myArray); ['a', 'c', 'd'];

Hope this helps. Reference: https://lodash.com/docs#compact

Answer 2

OK, imagine we have this array below:

const arr = [1, 2, 3, 4, 5];

Let's do delete first:

delete arr[1];

and this is the result:

[1, empty, 3, 4, 5];

empty! and let's get it:

arr[1]; //undefined

So means just the value deleted and it's undefined now, so length is the same, also it will return true...

Let's reset our array and do it with splice this time:

arr.splice(1, 1);

and this is the result this time:

[1, 3, 4, 5];

As you see the array length changed and arr[1] is 3 now...

Also this will return the deleted item in an Array which is [3] in this case...

Answer 3

you can use something like this

var my_array = [1,2,3,4,5,6];
delete my_array[4];
console.log(my_array.filter(function(a){return typeof a !== 'undefined';}));

Should display [1, 2, 3, 4, 6]

Answer 4

Array.remove() Method

John Resig, creator of jQuery created a very handy Array.remove method that I always use it in my projects.

// Array Remove - By John Resig (MIT Licensed)
Array.prototype.remove = function(from, to) {
  var rest = this.slice((to || from) + 1 || this.length);
  this.length = from < 0 ? this.length + from : from;
  return this.push.apply(this, rest);
};

and here's some examples of how it could be used:

// Remove the second item from the array
array.remove(1);
// Remove the second-to-last item from the array
array.remove(-2);
// Remove the second and third items from the array
array.remove(1,2);
// Remove the last and second-to-last items from the array
array.remove(-2,-1);

John's website

Answer 5

If the desired element to delete is in the middle (say we want to delete 'c', which its index is 1):

var arr = ['a','b','c'];

You can use: var indexToDelete = 1; var newArray = arr.slice(0, indexToDelete).combine(arr.slice(indexToDelete+1, arr.length))

Answer 6

IndexOf accepts also a reference type. Suppose the following scenario:

var arr = [{item: 1}, {item: 2}, {item: 3}];

var found = find(2, 3); //pseudo code: will return [{item: 2}, {item:3}]

var l = found.length;
while(l--) {
  var index = arr.indexOf(found[l])
  arr.splice(index, 1);
}

console.log(arr.length); //1

Differently:

var item2 = findUnique(2); //will return {item: 2}
var l = arr.length;
var found = false;
  while(!found && l--) {
  found = arr[l] === item2;
}

console.log(l, arr[l]);// l is index, arr[l] is the item you look for