How to run reindexing programmatically in magento 2

The blog is about how you can perform reindexing programmatically in Magento 2.

Please review below reindexing code and write code in any class(Helper, Block, Model, Controller) according to your requirements:

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/**
 * @var \Magento\Indexer\Model\IndexerFactory
 */
protected $_indexerFactory;
/**
 * @var \Magento\Indexer\Model\Indexer\CollectionFactory
 */
protected $_indexerCollectionFactory;

public function __construct(
    \Magento\Indexer\Model\IndexerFactory $indexerFactory,
    \Magento\Indexer\Model\Indexer\CollectionFactory $indexerCollectionFactory
){
   $this->_indexerFactory = $indexerFactory;
   $this->_indexerCollectionFactory = $indexerCollectionFactory;
}

public function runReIndexingProcess() {
   $indexerCollection = $this->_indexerCollectionFactory->create();
   $indexIDs = $indexerCollection->getAllIds();
	foreach ($indexIDs as $indexID) {
		$idx = $this->_indexerFactory->create()->load($indexID);
		//$idx->reindexRow($indexID); // you can run specific reindexRow according to your need
		$idx->reindexAll($indexID); // this reindexes all
	}
}

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Then, you need to call function runReIndexingProcess() to perform reindexing.