JSFiddle - React, Tailwind, and code Playground

JavaScript

function definedVar( string, containerVar ) {
	var splitted = string.split( "." );
	var testVar = containerVar;
	for( var i = 0; i < splitted.length; i++ ) {
		var propertyName = splitted[ i ];
		if( testVar[ propertyName ] == undefined ) {
			return false;
		}
		testVar = testVar[ propertyName ];
	}
	return true;
}
test = {
    prop1: "val1",
    prop2: {
        prop2_1: 'val2'
    }
};
alert( definedVar( 'prop1', test ) );
alert( definedVar( 'prop2.none' , test ));
alert( definedVar( 'prop2', test ) );
alert( definedVar( 'prop2.prop2_1', test ) );