Turning a 1D array and a variable into a new 2D array

Im new to programming and Im struggling with arrays in typescript.
I have the following variables:

let nameList: string[] = ['a', 'b', 'c', 'd'];
    let postId: number = 1;

My goal is to create a new 2D array:
let newList: (string | number)[][] = [];

where

newlist = [
      [a,1],
      [b,1],
      [c,1],
      [d,1]
    ]

I’ve tried:

for (let i: number = 0; i < userList.length; i++) {
      newList[i][0].push(userList[i]);
      newList[i][1].push(insertID);
    }

Also

for (let i: number = 0; i < userList.length; i++) {
      newList[i][0] = userList[i];
      newList[i][1] = insertID;
    }

Can someone help me with this?
Much apprerciated!

>Solution :

const new2dArray: [string, number][] = nameList.map((name) => [name, postId]);