从数组的所有键中，剔除掉数组原型上的公共属性和方法，只留下数字索引的TS工具

type ArrayIndices <T extends readonly any[]> = Exclude<keyof T, keyof any[]>;
let array = ["hello","word"] as const;
type ArrayIndexUnited = ArrayIndices<typeof array>; // typeof array: 获取array值的类型
// ArrayIndexUnited("0"|"1")