How to check if an Array is an Array of empty Arrays in Javascript

Question

In my node.js 6.10 app, I am trying to identify in my array looks like this:

[
    [
        []
    ],
    []
]

This nesting can go onto n level, and can have elements in arrays at any level. How can I do this? Thanks

PS I know I can do it using an level for loop, but was wondering about a more optimized solution.

Answer 1

An one-liner:

 let isEmpty = a => Array.isArray(a) && a.every(isEmpty); // let zz = [ [ [] ], [], [[[[[[]]]]]] ] console.log(isEmpty(zz)) 

If you're wondering how this works, remember that any statement about an empty set is true (" vacuous truth" ), therefore a.every(isEmpty) is true for both empty arrays and arrays that contain only empty arrays.

Answer 2

Yes,

All you need is to write recursive function, that checks array.length property on its way.

Something like that:

function isEmpty(arr) {
let result = true;

for (let el of arr) {
    if (Array.isArray(el)) {
        result = isEmpty(el); 
    } else {
        return false;
    }
}

return result;

}

You may consider to use lodash: https://lodash.com/docs/#flattenDeep

Answer 3

You can do:

 var arr = [[[]],[]], isEmpty = a => a.toString().replace(/,/g, '') === ''; console.log(isEmpty(arr)); 

Answer 4

另一个利用concat紧凑型解决方案：

[].concat.apply([], [[], [], []]).length; // 0