Events are not shown when adding events to array dynamically

Hi,

I am adding events dynamically to the calendar using string .

Here is the code for same ( this code is not working)
var eventstr = "{date: '"+ this.state.SelectedDate + "', hasEventCircle: {backgroundColor: '" + event1color +"'}}";
var event1 = [{eventstr}];
let updatedArray = this.state.eventItems.concat(event1);
this.setState({eventItems:updatedArray});

Whereas, if I declared event array like this then its showing properly.

var event1 = [{date: '2017-05-19', hasEventCircle: {backgroundColor: '#ccedcc'}}];
let updatedArray = this.state.eventItems.concat(event1);
this.setState({eventItems:updatedArray});

Can you please help me what is wrong with 1st approach ? How to construct the event string and add to the events array?

Thank you.