Use ES6 syntax instead of `for` loop

Question

I need to check if an array has any null value. If it does return false otherwise true.

How do I turn this

checkArray(array){
 for (var i = 0; i < array.length; i++) {
  if (array[i] === null || array[i] === '')
    return false;
 }
 return true;
}

into a working example with map and fat arrows?

I've tried this

checkArray(array){
  array.map(function(item) {
   if (item === null || item === '') {
     return false;
   } else {
     return true;
   }
  return true;
 })
}

But it always returns true. Why? Is it because map creates a new array?

it always returns undefined because you return nothing from checkArray — vp_arth
– vp_arth, Commented Apr 11, 2016 at 11:27
@vp_arth sorry I missed a bit. Check my edited code, but even then it always returns true — U r s u s
– U r s u s, Commented Apr 11, 2016 at 11:30
array.map should return [true, false, false, true] like array in your case. — vp_arth
– vp_arth, Commented Apr 11, 2016 at 11:34

zerkms · Accepted Answer · 2016-04-11 11:27:45Z

4

It's the good fit for the underutilised Array.prototype.some():

array.some(v => v === '' || v === null);

What it does is returns a boolean value that is true if the predicate is true for any of the array values, and false otherwise.

answered Apr 11, 2016 at 11:27

zerkms

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Comments

Dmitri Pavlutin · Accepted Answer · 2016-04-11 11:53:16Z

4

Another option is to use includes() method of the Array:

var isWithoutEmptyElements = !array.includes(null) && !array.includes('');

edited Apr 11, 2016 at 11:53

answered Apr 11, 2016 at 11:35

Dmitri Pavlutin

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5 Comments

vp_arth Over a year ago

your var should be named hasNotEmpty, isn't it?

Tushar Over a year ago

@DmitriPavlutin Error in logic? It should be arr.includes(null) || arr.includes(''). I need to check if an array has any null value.

Dmitri Pavlutin Over a year ago

@Tushar The method should return false if there is at least one null or empty string. The logic is correct.

vp_arth Over a year ago

Why not isThisArrayDoesNotContainAnyNullOrEmptyStringElements? =)

Dmitri Pavlutin Over a year ago

@vp_arth Next time :D

Tushar · Accepted Answer · 2016-04-11 11:28:26Z

1

The problem with the map variant is that nothing is returned from function.

A better way is to use Array#find

array.find(el => el === null || el === '');

var arr = [1, 23, 4, 'something', null, 3235, true];
var found = arr.find(el => el === null || el === '');
console.log(found); // null

answered Apr 11, 2016 at 11:28

Tushar

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Comments

Arun P Johny · Accepted Answer · 2016-04-11 11:30:44Z

1

In your code, you are using a .map(), it creates a new array with the values returned by the callback, but you are not returning any value from checkArray that is why you are getting undefined.

You want to make sure that none of the item is null or '' so use every()

checkArray(array) {
  return array.every((item) => item !== undefined && item !== '');
}

answered Apr 11, 2016 at 11:30

Arun P Johny

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Comments

Luka Jacobowitz · Accepted Answer · 2016-04-11 11:31:23Z

1

You're looking for reduce.

var found = array.reduce(function(acc, value) {
    if(acc){
        return true;
    }

    if (value === null || value === ''){
       return true;
    }

    return false;
}

answered Apr 11, 2016 at 11:31

Luka Jacobowitz

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5 Comments

vp_arth Over a year ago

some much better

Luka Jacobowitz Over a year ago

Agreed, didnt know ES6 had some.

zerkms Over a year ago

@LukaJacobowitz it actually was there in ES5 as well

Luka Jacobowitz Over a year ago

Even more embarrassing :D

zerkms Over a year ago

@LukaJacobowitz yep, that's why I called it "underutilised" - because for some magical reason people tend to not knowing about it at all :-) (and it's fine though)

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