CODEWITHSUNDEEP
javascript
user985409
user985409

Reputation: 1385

how to check if var is null when it can be array of nulls

There is a var that can be either an integer or an array of integers. I want to have a check that returns true when the var is not null or its array elements are null. The var can be:

a = null

or

a = [null, null]

The check 

if (a != null)

returns true when

a = [null, null]

I want to avoid this. How can I do it in javascript, preferrably coffescript.

Upvotes: 0

Views: 77

Answers (4)

Christoph
Christoph

Reputation: 968

Well, I guess it depends on whether a single null in the array is sufficient to fail the check. E.g, is [1,3, 5, null, 9] sufficient for that IF check above to return true? If so, then the suggestions above will work. If not, then you'll probably want to do something like this:

Array.prototype.unique =  [].unique || function (a) {
    return function () { 
      return this.filter(a)
    };
}(function(a,b,c) {
    return c.indexOf(a,b + 1) < 0
});
var nullArray = [null, null, null, null],
    notNullArray = [null, 1, null, 2],
    filtered;

if(( filtered = nullArray.unique()) && (filtered.length == 1) && (filtered[0] == null)) {
    // NULL VALUE
    alert( 'NULL!')
} else {
    // SAFE TO WORK WITH
    alert('NOT NULL!')
}

if(( filtered = notNullArray.unique()) && (filtered.length == 1) && (filtered[0] == null)) {
    // NULL VALUE
    alert( 'NULL!')
} else {
    // SAFE TO WORK WITH
    alert('NOT NULL!')
}

If the length is more than 1 then it's definitely not containing only nulls.

thnx,
Christoph

Upvotes: 0

Tuhin
Tuhin

Reputation: 3373

if (a instanceof Array) {
   //check each index of a
} else {

    //check only the a
}

Upvotes: 0

user985409
user985409

Reputation: 1385

I used if (a.indexOf(null) == -1) from elclanrs . Thank you!

Upvotes: 1

Hemant Metalia
Hemant Metalia

Reputation: 30638

you can check it as follow: following conditions will be required to test

if(a != null)

if (typeof a[index] !== 'undefined' && a.indexOf(null) == -1) 

if (a[index] != null)

Upvotes: 0

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