kotlin-stdlib / kotlin.collections / AbstractMutableList / lastIndexOf lastIndexOf Common 1.0 open fun lastIndexOf(element: @UnsafeVariance E): Int(source) JS Native 1.1 open fun lastIndexOf(element: E): Int(JS source) (Native source) Returns the index of the last occurrence of the specified element in the list, or -1 if the specified element is not contained in the list.