client/components/tinymce/plugins/wpemoji/plugin.js
function parseNode( node ) {
		let selection, bookmark;

		if ( node && twemoji.test( node.textContent || node.innerText ) ) {
			if ( env.webkit ) {
				selection = editor.selection;
				bookmark = selection.getBookmark();
			}

			replaceEmoji( node );

			if ( env.webkit ) {
				selection.moveToBookmark( bookmark );
			}
		}
	}
function parseNode( node ) {
		let selection, bookmark;

		if ( node && twemoji.test( node.textContent || node.innerText ) ) {
			if ( env.webkit ) {
				selection = editor.selection;
				bookmark = selection.getBookmark();
			}

			replaceEmoji( node );

			if ( env.webkit ) {
				selection.moveToBookmark( bookmark );
			}
		}
	}
Test if the node text contains emoji char(s) and replace.