Check if it is empty regardless of type, javascript

Question

I am trying to create a function that checks if you have something blank, empty, Undefined, null etc..

But my difficulty is that I don’t know all the ways a string is "blank"

I created this function

function empty() {
   var args = [].slice.call(arguments);

    args.forEach(function(argument) {
        if(!argument || 0 === argument.length || !argument || /^\s*$/.test(argument) || argument.length === 0 || !argument.trim()) {
            return false;
        } 
    });
}

the intention is to return false so that I can simply check if among my variables there are any blank ones in this way if(!empty(var1, var2...)) {

But there are several ways, as I said, for example in my doubts:

If it is an array, how to know if it is empty?

If it is a JSON how to know if it is empty?

If it’s just numbers, you can tell if it’s empty?

are so many ways you have to check that I get lost..

When I say empty I mean Undefined, null, filled only with empty spaces etc..

Answer 1

There is no "empty" value for numbers and booleans, unless you define some. This "empty" value, in these cases, would be null, or undefined.

I’m assuming that:

• null is empty;
• undefined is empty;
• objects without fields is empty (including inherited);
• arrays without elements is empty;
• strings of size 0 are empty;
• strings formed only by blank characters are empty;
• there is no specific numerical or boolean value to represent empty (could be 0 or false, maybe).

Thus, it could be written as follows:

function empty() {
    var args = Array.prototype.slice.call(arguments);

    return args.some(function(argument) {
        return argument === null
            || typeof argument === "undefined"
            || (Array.isArray(argument) && argument.length === 0)
            || (typeof argument === "object" && emptyObject(argument))
            || (typeof argument === "string" && (argument.length === 0 || argument.trim().length === 0));
    });
}

function emptyObject(arg) {
    var count = 0;
    for ( var i in arg ) {
        count++;
        break;
    }
    return count === 0;
}

The method emptyObject checks how many fields an object has. I don’t know any other way to do this.

The call to the method Array.some serves so that when a single empty item is found, the method already returns, not checking all other items.

Not tested, so there may be some errors ;D

Improvements are welcome!

Answer 2

In Javascript, the fastest way to validate the result of an expression including the most commonly used types of values representing a nonvalue is the double negation. More details on this reply.

The possible values that can suffer Typecast for true/false are:

• false
• NaN
• undefined
• null
• "" (empty string)
• 0

Some examples of validation via double negation (taken of this answer):

          !!false === false
           !!true === true

              !!0 === false
!!parseInt("foo") === false // NaN
              !!1 === true
             !!-1 === true  // -1 é verdadeiro

             !!"" === false // string vazia é 'falsa'
          !!"foo" === true  // string não-vazia é 'verdadeira'
        !!"false" === true  // ...mesmo se conter o valor "false"

     !!window.foo === false // undefined é falso
           !!null === false // null também

             !!{} === true  // um objeto vazio é 'verdadeiro';
             !![] === true  // um array vazio também.