What is the best way to test for an empty string with jquery-out-of-the-box?

Straightforward checks for empty and whitespace strings

The zero-fuss route: The trim and not dance

A straightforward approach to detect if a string is empty or filled with mischievous white spaces is:

if (!yourString.trim()) {
  // You shall not pass, Mr. Whitespace!
}


The handy trim() method takes care of the whitespaces around your string.

Pondering about 'null' and 'undefined'

Before you run your victory lap, remember, null or undefined values also get flagged here:

let lonelyVariable = null;
if (!lonelyVariable) {
  // The emptiness within these brackets is where loneliness, 
  // I mean 'null' and 'undefined', dwell!
}


Meaning, if you want to be kind and allow null, you have to alter your condition a bit:

if (lonelyVariable !== "") {
  // Hey null, I see you, and I accept you!
}


Playing safe with the 'senior' browsers, using $.trim

Older browsers lacking trim method can give you some unexpected surprises. To keep surprises at bay, you can use jQuery's $.trim:

if (!$.trim(lonelyVariable)) {
  // As long as there's jQuery, 'no trim support' can't rain on your parade!
}


Enhancing readability and handling edge cases efficiently

Implementing an isEmpty utility function

For improved readability and consistency, consider encapsulating your check in an isEmpty function:

function isEmpty(str) {
  return !str.trim();
}

if (isEmpty(yourString)) {
  // Seems like our string took an early day off!
}


Now the logic is centralized, promoting maintainability!

Dealing with non-string values

What's that? Your «string» turned out to be an imposter? Fear not, prepare your conditions:

if (typeof yourString === 'string' && !yourString.trim()) {
  // Ah-ha! Caught you, Mr. Imposter!
}


Boom! You're now safe from runtime errors

Verifying 'emptiness' with the length property

A little more assurance never hurts. Check the length to be 100% sure:

if (yourString.trim().length === 0) {
  // Our string is barren as a desert!
}


No characters, no worries!

Harnessing the power of 'falsy' in JavaScript

In JavaScript, null, undefined, NaN, 0, -0, false, and empty strings are all falsy. This comes in handy for quick evaluations:

if (!yourString) {
  // Hello emptiness, my old friend!
}


Yes, it's as simple as that!

JQuery and its falsehood nuances

Distinguishing an empty string from other falsy values

In the rare event where an empty string needs to be isolated from other falsy values like null or undefined, use direct comparison:

if (yourString === "") {
  // That's an empty string, not null or undefined! 
  // A 'sort of' victory for our string!
}


Dear empty string, enjoy your individuality!