index.js
function isCustomFrontMatter( attr ) {

	if ( attr !== 'title' && attr !== 'category' && attr !== 'content' &&
		attr !== 'created' && attr !== 'excerpt' && attr !== 'updated' ) {

		return true;

	} else {

		return false;
	}
}
function isCustomFrontMatter( attr ) {

	if ( attr !== 'title' && attr !== 'category' && attr !== 'content' &&
		attr !== 'created' && attr !== 'excerpt' && attr !== 'updated' ) {

		return true;

	} else {

		return false;
	}
}
function isCustomFrontMatter ( attr ) { if ( attr !== 'title' && attr !== 'category' && attr !== 'content' && attr !== 'created' && attr !== 'excerpt' && attr !== 'updated' ) { return true ; } else { return false ; } }
Check if front matter attribute is custom or not

@param {string} attr The attribute name
@returns {boolean}
Check if front matter attribute is custom or not