[React]Add or push values to array defined in state

var newArr = this.state.arr.concat('new value');
this.setState({ myArray: newArr });

//USING es6 IT CAN BE DONE PRETTY EASILY

//PUSH ITEM TO THE END OF AN ARRAY
this.setState({
    arr: [...this.state.arr, "new value"]
});

//ADD NEW ARRAY AS A LAST ELEMENT
this.setState({
    arr: [...this.state.arr, ["a", "b", "c"]]
});

//PUSH OBJECT OR ITEM TO THE START OF ARRAY
this.setState({
    arr: [{"name": "value"}, ...this.state.arr]
});