Javascript TypeScript：具有不同元素类型的concat数组

这是有效的

let head = [["title", "value"], ["a", 1]];
let tail = [["b", 2], ["c", 3]];

let all = head.concat (tail);

好的结果是

[["title", "value"], ["a", 1], ["b", 2], ["c", 3]]

但我需要的是这个，而这不起作用

let head = [["title", "value"]];
let tail = [["a", 1], ["b", 2], ["c", 3]];

let all = head.concat (tail);

错误：

Argument of type '(string | number)[][]' is not assignable to parameter 
of type 'string[] | string[][]'. 
 Type '(string | number)[][]' is not assignable to type 'string[][]'. 
  Type '(string | number)[]' is not assignable to type 'string[]'. 
   Type 'string | number' is not assignable to type 'string'. 
    Type 'number' is not assignable to type 'string'.

如果我将尾部的数字转换成字符串，它就会起作用——因为某些原因，我无法做到这一点

那么我怎样才能让它工作

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谢谢

您可以这样声明

头的类型：

let head: [Array<string|number>] = [["title", "value"]];

let head:[Array]=[[“title”，“value”]；

这将消除错误并保持类型安全