How do you filter javascript nested arrays without key

This approach requires iterating over the array twice by first filtering out the invalid elements and then mapping over the array to pluck out the name.

Note that this is leveraging array destructuring which allows us to nicely give the value at a given index a name, rather than trying to remember the index offset and what it means.

const data = [
  ["Ahmed", 8],
  ["Clement", 10],
  ["Elamin", 6],
  ["Adam", 7],
  ["Tayoa", 11],
  ["Nina", 10],
  ["Bob", 9],
  ["Lee", 1]
]

const filtered = data.filter(([_name, num]) => num > 8).map(([name]) => name)

console.log(filtered)

You can reduce() the array in one pass by checking if the second element in the array (age?) is more than 8, if so, add the first element in the array (the name) to the accumulator array, like so:

let arr = [
  ["Ahmed", 8],
  ["Clement", 10],
  ["Elamin", 6],
  ["Adam", 7],
  ["Tayoa", 11],
  ["Nina", 10],
  ["Bob", 9],
  ["Lee", 1],
];

let result = arr.reduce((acc, [name, age]) => (age > 8 && acc.push(name), acc), []);

console.log(result);