JavaScript Creating array in object and push data to the array -

i'm new programming. i'm trying react , have function addcomment executed when user adds comment news.i need create in moment property comments (array) , assign or push array inputcommentvalue value. right rewrite 0 element of array , can't add new element. can please tell me put push method? thank you!

var articles = [{   title: "sit amet erat",   text: "nam dui proin leo odio porttitor id consequat in consequat ut nulla sed accumsan"  }, {   title: "pulvinar sed",   text: "velit id pretium iaculis diam erat fermentum justo nec condimentum" }]    addcomment(index, inputcommentvalue){ articles = [...articles], articles[index].comments=[inputcommentvalue]; this.setstate({articles:articles}); } 

assuming data exist in component's state , handler that

addcomment(index, inputcommentvalue){     // copy array , not mutate state     let articles = [...this.state.articles];     // check if comments not exist     if(!articles[index].comments) articles[index].comments=[];     // add new comment array     articles[index].comments.push(inputcommentvalue);     // update component new articles     this.setstate({articles:articles}); }