1. Add an array into the root array.

2. Add an object into the nested array.

let dataObj: { content: any;[key: string]: any }[][] = [];

for (let i = 0; i < data.length; i++) {
   dataObj.push([]);

   for (let j = 0; j < data[i].length; j++) {
      dataObj[i].push({ content: data[i][j] })
   }
}

Alternatively, you can work with .map().

let dataObj: { content: any;[key: string]: any }[][] = [];

dataObj = data.map(x => 
  x.map(y => {
    return { "content": y };
  })
);

Sample TypeScript Playground

1. Add an array into the root array.

2. Add an object into the nested array.

let dataObj: { content: any;[key: string]: any }[][] = [];

for (let i = 0; i < data.length; i++) {
   dataObj.push([]);

   for (let j = 0; j < data[i].length; j++) {
      dataObj[i].push({ content: data[i][j] })
   }
}

Alternatively, you can work with .map().

let dataObj: { content: any;[key: string]: any }[][] = [];

dataObj = data.map(x => 
  x.map(y => {
    return { content: y };
  })
);

Sample TypeScript Playground