Array.prototype.entries()

entries() 方法會回傳一個包含陣列中每一個索引之鍵值對（key/value pairs）的新陣列迭代器（Array Iterator）物件。

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a.entries()

一個新的 Array 迭代器物件。

var a = ['a', 'b', 'c'];
var iterator = a.entries();

for (let e of iterator) {
  console.log(e);
}
// [0, 'a']
// [1, 'b']
// [2, 'c']

• Array.prototype.keys()
• Array.prototype.values()
• Array.prototype.forEach()
• Array.prototype.every()
• Array.prototype.some()
• for...of
• 迭代協議