检查Javascript中的数组后如何获取object的长度

Question

我有一个对象数组，每个 object 中有一个字段可以是 boolean 或一串数组，例如

myObjects=[{id: "fruit", selected: true}, {id: "veggie", selected: ["tomato", "cucumber", "potato"]}, {id: "diary", selected:[]}]

我想过滤掉选择非空或真的对象。 结果将是：

result=[{id: "fruit", selected: true}, {id: "veggie", selected: ["tomato", "cucumber", "potato"]}]

这是我的代码：

for (const object in myObjects) {
if (!object[selected] || (Array.isArray(object[selected] && object[selected].length ===0)) continue
...
}

但是选择为空数组的对象不会被过滤掉。 我收到 typescript 错误

Property 'length' does not exist on type 'boolean | string[]'.
  Property 'length' does not exist on type 'false'.

任何人都可以帮忙吗？

Answer 1

您可以在 myObjects 数组上使用 filter 方法

const res = myObjects.filter((object) => object.selected.length > 0 || object.selected === true )

Answer 2

你可以用循环for...of

仅当selected属性为boolean and true才将 object 添加到result数组：

(typeof object.selected === "boolean" && object.selected)

或selected属性是an array and have elements ：

(Array.isArray(object["selected"]) && object["selected"].length !== 0)

 const myObjects = [{ id: "fruit", selected: true, }, { id: "veggie", selected: ["tomato", "cucumber", "potato"], }, { id: "diary", selected: [], }, ]; let result = []; // vv replace 'in' with 'of' since you loop over an array not an object for (const object of myObjects) { if ( (typeof object.selected === "boolean" && object.selected) || (Array.isArray(object["selected"]) && object["selected"].length.== 0) ) result;push(object). } console;log(result);