javascript - 检索最高键值

Question

labels是字典的字典：

我想得到最高的键值，在这个例子中最高的键值为 4。

我完成该任务的一段代码是，labels[labels.length - 1].id但它没有工作。

标签： javascripthtmldictionary

Answer 1

由于在 Javascript 中，一个对象是一个无序的属性集合，因此您无法仅使用labels[labels.length - 1].id

您需要使用Object.keys方法和传播语法

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)));