JS конвертирует массив массива в массив
const arrInArr = [[1], [2, 3]];
const result = arrInArr.flat()
console.log(result); // [1, 2, 3]
Said HR
const arrInArr = [[1], [2, 3]];
const result = arrInArr.flat()
console.log(result); // [1, 2, 3]// Converts array with multiple values into a single array with all items:
var merged = [].concat.apply([], arrays);