javascript - 检索最高的键值

Question

labels 是字典的字典:

我想获取最高的键值，在本例中最高的键值是4。

我实现该任务的代码是labels[labels.length - 1].id，但它不起作用。

Answer 1

由于在 Javascript 中，对象是无序属性集合，因此仅使用 labels[labels.length] 无法找到 max 键- 1].id

您需要使用Object.keys方法和spread syntax

let labels = {"1":{"id":"1","image":"1-0.png","name":"","xMax":"4802","xMin":"4770","yMax":"156","yMin":"141"},"2":{"id":"2","image":"1-0.png","name":"","xMax":"4895","xMin":"4810","yMax":"157","yMin":"141"},"3":{"id":"3","image":"1-0.png","name":"","xMax":"4923","xMin":"4903","yMax":"156","yMin":"145"},"4":{"id":"4","image":"1-0.png","name":"","xMax":"4956","xMin":"4931","yMax":"156","yMin":"145"}}

console.log(Math.max(...Object.keys(labels)));