How can I check if a variable is empty or undefined within an array using JavaScript or Jquery

Question

So I have an array that I created but I would like to execute an action if one or more variables are empty in my array.

jQuery(document).ready( function($) {

        var fields = ["", "two", "three", "four", "five"];


        if (fields.length === 0) {
            alert('One or more variables are empty!');
        }

        else {
          alert('All variables are here!');
        }    


   });

I know this code above is wrong because it will always launch the latter.

So basically

var fields = ["", "two", "three", "four", "five"];

Should return One or more variables are empty!

And this:

 var fields = ["one", "two", "three", "four", "five"];

Should return All variables are here!

mhodges · Accepted Answer · 2017-05-10 21:01:18Z

One way to do it would be to use Array.prototype.every(). One thing that's nice about every() is that if a single element returns falsey, it will short-circuit the array iteration, meaning that it will not continue to unnecessarily process the remaining elements in the array.

var fields = ["", "two", "three", "four", "five"]; // invalid array
var fields2 = ["one", "two", "three", "four", "five"]; // valid array

function validateFields (fields) {
  var everyFieldIsValid = fields.every(function (field) {
    // ensure there are no gaps in the array and that each element is not
    // undefined, null, or equal to empty string ("")
    return field != null && field !== "";
  }); 
  
  if (everyFieldIsValid) {
    // success logic goes here - you can console.log, alert, return true/false, etc.
    return "All variables are here!";
  }
  else {
    // failure logic goes here - you can console.log, alert, return true/false, etc.
    return "One or more variables are empty!";
  }
}

console.log(validateFields(fields));
console.log(validateFields(fields2));

A very simple solution. I never thought of this. Will try it now!

Egor Stambakio · Accepted Answer · 2017-05-10 21:11:58Z

2

You can check if every array element conforms to your condition using a function Array.prototype.every:

var fields = ["", "two", "three", "four", "five"];

var res = fields.every(f => f != null && f.length) ? 'all here' : 'some are empty';

console.log(res)

every(f => f != null && f.length) checks if every element is defined, not equal to null and has length > 0. res is assigned an answer depending on this condition (ternary operator is used instead of if to make the code more clear).

edited May 10, 2017 at 21:11

answered May 10, 2017 at 20:53

Egor Stambakio

18.2k5 gold badges37 silver badges35 bronze badges

1 Comment

mhodges Over a year ago

"ternary operator is used instead of if to make the code more clear"... said no one ever...

Victor Garcia · Accepted Answer · 2017-05-10 20:54:37Z

0

Do this:

 fields.filter(function(object){
        return object.trim().length > 0;
    });

this will delete all the empty fields. Simply add conditionnal if you want to know is there is a empty field!

answered May 10, 2017 at 20:54

Victor Garcia

54 bronze badges

1 Comment

mhodges Over a year ago

This code makes a lot of assumptions.. 1. Assuming every element in the array is a string, and there are no "holes" in the array, 2. Assuming the OP wants to remove the empty elements I am pretty sure neither one of those assumptions are accurate, but you should ask the OP for clarification.

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