Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | 1x 2621x 1x 2620x 1x 2619x 2619x 2619x 2619x 545x 2619x 1x | /** ****************************************************************************************************
* File: neighbor.js
* Project: geohash
* @author Nick Soggin <iSkore@users.noreply.github.com> on 19-Feb-2019
*******************************************************************************************************/
'use strict';
const
{
BASE32,
NEIGHBOR_CODEX,
BORDER_CODEX
} = require( './variables' );
/**
* Determines neighbor cell in given direction.
*
* @param {string} geohash - Cell to which neighbor cell is required.
* @param {string} direction - Direction from geohash (N/S/E/W).
* @returns {string} Geocode of neighbor cell.
* @throws Invalid geohash.
*/
function neighbor( geohash, direction ) {
if ( geohash.length === 0 ) {
throw new Error( 'Invalid geohash' );
}
else if ( 'nsew'.indexOf( direction ) === -1 ) {
throw new Error( 'Invalid direction' );
}
const
lastCh = geohash.slice( -1 ),
type = geohash.length % 2;
let parent = geohash.slice( 0, -1 );
if ( BORDER_CODEX[ direction ][ type ].indexOf( lastCh ) !== -1 && parent !== '' ) {
parent = neighbor( parent, direction );
}
// append letter for direction to parent
return parent + BASE32.charAt( NEIGHBOR_CODEX[ direction ][ type ].indexOf( lastCh ) );
}
module.exports = neighbor;
|