lastIndexOf

Return the index of the last element which equals a provided search element.

Usage

var lastIndexOf = require( '@stdlib/array/base/last-index-of' );

lastIndexOf( x, searchElement, fromIndex )

Returns the index of the last element which equals a provided search element.

var x = [ 1, 2, 3, 4, 5, 6 ];

var idx = lastIndexOf( x, 3, 5 );
// returns 2

If the function is unable to find an element which equals a provided search element, the function returns -1.

var x = [ 1, 2, 3, 4, 5, 6 ];

var idx = lastIndexOf( x, 7, 5 );
// returns -1

To begin searching from a specific index, provide a corresponding fromIndex argument.

var x = [ 1, 1, 2, 1, 2, 3, 3 ];

var idx = lastIndexOf( x, 2, 3 );
// returns 2

If fromIndex is less than zero, the starting index is resolved relative to the last array element, with the last array element corresponding to fromIndex = -1.

var x = [ 1, 1, 2, 1, 2, 3, 3 ];

var idx = lastIndexOf( x, 2, -4 );
// returns 2

Notes

• The function scans an input array from the starting index to the beginning of the array (i.e., backward).

• If provided an array-like object having a lastIndexOf method, the function defers execution to that method and assumes that the method API has the following signature:

  x.lastIndexOf( searchElement, fromIndex )
  

• If provided an array-like object without a lastIndexOf method, the function performs a linear scan and returns immediately upon finding a match.

• When searching for a search element, the function checks for equality using the strict equality operator ===. As a consequence, NaN values are considered distinct, and -0 and +0 are considered the same.

Examples

var lastIndexOf = require( '@stdlib/array/base/last-index-of' );

var x = [ 'foo', 'bar', 'beep', 'boop', 'foo', 'bar' ];

var idx = lastIndexOf( x, 'beep', 5 );
// returns 2

idx = lastIndexOf( x, 'bop', 5 );
// returns -1

idx = lastIndexOf( x, 'foo', 5 );
// returns 4

idx = lastIndexOf( x, 'foo', -3 );
// returns 0

idx = lastIndexOf( x, 'foo', -50 );
// returns -1