段落ブロックに日付・時刻の入力支援を実装した

function setDateTimeCompleter( completers, blockName ) {
	return blockName === 'core/paragraph' ?
		[ ...completers, datetimeCompleter ] :
		completers;
}

wp.hooks.addFilter(
	'editor.Autocomplete.completers',
	'core-ex/autocompleters/datetime',
	setDateTimeCompleter
);

var datetimeCompleter = {
	name: 'datetime',
	triggerPrefix: 'now',
	options: [
		{ format: 'Y/m/d' },
		{ format: 'Y年n月j日' },
		{ format: 'm/d' },
		{ format: 'n月j日' },
		{ format: 'H:i:s' },
		{ format: 'H時i分s秒' },
		{ format: 'H:i' },
		{ format: 'H時i分' },
		{ format: 'Y/m/d H:i:s' },
		{ format: 'Y年n月j日 H時i分s秒' },
	],
	getOptionKeywords: function ( option ) {
		return return option.format.replace( /[^a-z\s]/gi, '' ).split( /\s+/g ).
			concat( Array.from( option.format.replace( /[^a-z]/gi, '' ) ) );
	},
	getOptionLabel: function ( option ) {
		return this.getOptionCompletion( option );
	},
	getOptionCompletion: function ( option ) {
		const now = new Date();
		const datetime = now.toLocaleString().match(/(\d{4})\/(\d{1,2})\/(\d{1,2})\s(\d{1,2}):(\d{1,2}):(\d{1,2})/i);
		return option.format.
			replace( 'Y', datetime[1] ).
			replace( 'm', ( '0' + datetime[2] ).slice( -2 ) ).
			replace( 'n', datetime[2] ).
			replace( 'd', ( '0' + datetime[3] ).slice( -2 ) ).
			replace( 'j', datetime[3] ).
			replace( 'H', datetime[4] ).
			replace( 'i', datetime[5] ).
			replace( 's', datetime[6] );
	},
};