How to check if an array is empty or exists?

Nitty-gritty array detection

When working with arrays, beware of the traps and pitfuls. Here's a deep-dive into array validation and handling all possible corner cases.

Asserting array type

if (!Array.isArray(image_array)) {
  console.error("Houston, we've got a problem! It's not an array!");
}
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Don't trust external data

Data from external sources, e.g., server-side response or an API, should be handled with care:

// Believe nothing, trust no one.
var image_array = JSON.parse(phpJsonEncodedArray || '[]');
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Avoiding accidental redeclaration

Redeclaring variables should be avoided, or it may result in unexpected behaviour, you don't want unexpected "surprises", do you?

// Reuse, reduce, recycle.
var image_array = image_array || [];
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Managing data-loaded actions

Deal with critical actions that depend on the existence of array and its element count. For instance, loading images from an array:

if (Array.isArray(image_array) && image_array.length) {
  // Queue the red carpet. Our star image has arrived!
  loadImage(image_array[image_array.length - 1]);
} else {
  alert("Image array is on a vacation. 🏖️");
}
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Array anomalies and avoidance strategies

Be super prepped for unpredictable data, the silent destroyers of logic. Guilty as charged, arrays have some quirks:

1. Coquettish array length

Just like cats, undefined and null have no length. Be cautious!

if (yourArray && yourArray.length > 0) {
  // Array is alive and kicking!
} 
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2. Variable hoisting - A magic trick gone wrong

Avoid variable hoisting (JavaScript's magic trick!) by using let or const for proper block scoping:

// Now you see it, now you don't.
let yourArray = []; 
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3. Support the elders - Older JavaScript environments

Support developers stuck in the JavaScript Jurassic period (ES5 and below):

// Dinosaur-friendly syntax.
if (yourArray && yourArray.length) {
  // Array exists and is not empty
}
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4. The grand entrance - On page load instances

A foolproof strategy for handling array-based operations at page load event:

// Lights, camera, action! 
window.onload = function() {
  if (image_array && image_array.length) {
    loadImage(image_array[0]);
  } 
};


Critical observations

Detect or regret

When checking arrays, stay away from ambiguous checks like if (array) that only verify existence and not emptiness:

// False positives are worse than no positives.
if(yourArray !== undefined && yourArray !== null) { yourArray.length }
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Variable declaration - Stick to the basics

Stick with var, let, or const to declare your variables in Javascript. The accidental global vars are no fun:

// You cannot not communicate, right?
let image_array = image_array || [];
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Initialization - Stay on the safe side.

Stay vigilant when initializing arrays from server-side data. Always parse or verify the data structure:

// Spoiler: Data can't be trusted.
const data = Array.isArray(serverData) ? serverData : [];
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To wrap it up

Always test your code with different array states (empty, filled, null, undefined). Reliability is bliss!