var element = document.getElementsByTagName("a-sphere");
//a-sphereの要素を所得し、elementに配列として入れる[1つ目の<a-sphere>,２つ目の<a-sphere>]

element[0].addEventListener("click", function() {
  location.href = "https://www.tsuruokakanko.com/spot/275";
},false);

element[1].addEventListener("click", function() {
  location.href = "https://www.pref.yamagata.jp/110001/sangyo/sangyoushinkou/him_top/him_maincat4/him_03.html";
},false);