How to flatten array in jQuery?

Question

How to simply flatten array in jQuery? I have:

[1, 2, [3, 4], [5, 6], 7]

And I want:

[1, 2, 3, 4, 5, 6, 7]

Answer 1

You need arr.flat([depth])

var arr1 = [1, 2, [3, 4]];
arr1.flat(); 
// [1, 2, 3, 4]

var arr2 = [1, 2, [3, 4, [5, 6]]];
arr2.flat();
// [1, 2, 3, 4, [5, 6]]

var arr3 = [1, 2, [3, 4, [5, 6]]];
arr3.flat(2);
// [1, 2, 3, 4, 5, 6]

Answer 2

Use the power of JavaScript:

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

console.log( Array.prototype.concat.apply([], a) );
//will output [1, 2, 3, 4, 5]

Answer 3

Old question, I know, but...

I found this works, and is fast:

function flatten (arr) {
  b = Array.prototype.concat.apply([], arr);
  if (b.length != arr.length) {
    b = flatten(b);
  };

  return b;
}

Answer 4

You can use jQuery.map():

callback( value, indexOrKey )The function to process each item against. The first argument to the function is the value; the second argument is the index or key of the array or object property. The function can return any value to add to the array. A returned array will be flattened into the resulting array. Within the function, this refers to the global (window) object.