Array.prototype.lastIndexOf()

The lastIndexOf() method of Array instances returns the last index at which a given element can be found in the array, or -1 if it is not present. The array is searched backwards, starting at fromIndex.

The lastIndexOf() method compares searchElement to elements of the array using strict equality (the same algorithm used by the === operator). NaN values are never compared as equal, so lastIndexOf() always returns -1 when searchElement is NaN.

The lastIndexOf() method skips empty slots in sparse arrays.

The lastIndexOf() method is generic. It only expects the this value to have a length property and integer-keyed properties.

Syntax example: lastIndexOf(searchElement)