Bug in older Safari browsers

[Lumeriol]

On Safari 13 and older, there is syntax error in code:
SyntaxError: Unexpected token '='. Expected an opening '(' before a method's parameter list.

Problems are with this code

init = () => {
	this.removeBySelector('.happy-radio');
	this.removeBySelector('.happy-checkbox');

	this.initRadio();
	this.initCheckbox();
}
``` and similars, because public field declarations are not supported up to Safari 14.1.

And as a dependent library for DataGrid it could not be used on older Apple devices.