js遍歷物件的方法
阿新 • • 發佈:2019-01-22
1. for ... in 語句
for (let variable in object) { ... }
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Statements/for...in
以任意次序迭代一個物件的可列舉屬性。
var obj = {a: 1, b: 2};
for (let i in obj) {
console("key:" + i + ", value:" + obj[i]);
}
陣列Array的遍歷,i則為數字
2. 迭代器遍歷
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Iterator
如Array
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
arr.forEach((value, index) => {
console.log(value);
});
3. for ... of 語句
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Statements/for...of
for...of語句在可迭代物件(包括 Array, Map, Set, String, TypedArray,arguments 物件等等)上建立一個迭代迴圈,對每個不同屬性的屬性值,呼叫一個自定義的有執行語句的迭代掛鉤.
但對於普通物件是不適應的。原因是沒有實現參考下文。
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Guide/iterable