1.  Array.prototype.slice.call()    轉陣列再遍歷

var a= document.querySelectorAll('div');
var arr = Array.prototype.slice.call(a);
console.log(arr);

 2.Array.from() 將類陣列轉為陣列

var a= document.querySelectorAll('div');
var arr = Array.from(a);
arr.forEach(function(i){
　　console.log(i);
})

 3.for of

let elements = document.querySelectorAll('div');

for (let element of elements) {
  console.log(element.tagName);
}