Remove first item of array of array

Try to use JavaScript built-in function shift().

var a = [[1,2], [3,4,5]];

a.map(item => { 
    item.shift();
    return item;
});

console.log(a); // [[2], [4, 5]]

Official guide: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/shift

You can use map and splice:

const a = [[1,2], [3,4,5]];

console.log(
  a.map(item => item.splice(1))
)

Basically you're mapping each item of the array with the same array without the first element (since splice mutate the array).

If you want have a copy also of the inner array, then you should use slice instead.

Loop through the main array as you normally would, like

    let array = [[1,2], [3,4,5]]
    for (let el of array) {
         // Now you'll be accessing each array inside the main array,
         // YOu can now remove the first element using .shift()
         el.shift();
     }

You can map the array, and got all items, but the the 1st, with Array.slice():

const arr = [[1,2], [3,4,5]];

const result = arr.map(item => item.slice(1));

console.log(result);

Try this :

var arr = [[1,2], [3,4,5]];

for (var innerArray of arr) {
  // Using array.splice()
  for (var element of innerArray) {
  	if (element === 1 || element === 3) innerArray.splice(innerArray.indexOf(element), 1);
  }
}

console.log(arr);