JavaScript: Add and remove from arrays / arrays as collections

Did you know you can easily add and remove elements from Javascript arrays ?

Declare an array:

var arr = [];

To add an element:

arr.push(item);

To remove an element at index idx:

arr.splice(idx, 1);

To remove an element elm:

var idx = arr.indexOf(elm);

if (idx > -1) arr.splice(idx, 1);

The splice function allows adding and removing items from an array by providing a range (start index and length) and replacement values.

See also: https://www.w3schools.com/jsref/jsref_splice.asp