in frontend/src/containers/Home.js [168:180]
handleImgPrev() {
const curidx = this.state.selectedImg;
const maxidx = this.state.imglist.length - 1;
var nextidx = curidx - 1;
if(nextidx < 0) {
console.log("going back to max");
nextidx = maxidx;
}
else {
console.log("decrementing");
}
this.setState({ selectedImg: nextidx});
}