Falsy and Truthy and empty arrays in ServiceNow Javascript

[Andy-L]

As we know, GlideElements and other types of Glide objects can  be interpreted as false (falsy) depending on their underlying value, e.g.

if (incident_gr.active) { ... }

Even though the Javascript standard says the only things that are falsy are: false, 0, -0, 0n, "", null, undefined, NaN, and document.all. Until recently, I had assumed this was because Glide objects are not really JavaScript objects - but something else -  Java objects etc. However, the other day I was reviewing some code that I only wanted to run if a pure Javascript array object had at least one element:

var someArray = [];

callSomeFunctionThatMightAddElementsTo(someArray);

if (someArray) { 
    doSomething(); 
} 

Despite appearing wrong, from a pure JavaScript perspective (as an array is always Truthy according to the Javascript Specification), it worked perfectly! It should have been...

if (someArray && someArray.length ) { 
    doSomething(); 
}

Why didn't I need to change it? It appears that, in Server-Side JS, the empty array [] is also treated as false (contrary to the Standard).

For example, the following code outputs 'truthy' in the Browser dev console (client side), but 'falsy' in a background script.

console.log( [] ? 'truthy' : 'falsy' );

Just something to be aware of I guess! Especially if switching between client-side and server-side scripting. I've put up some notes here: Truthy/Falsy behaviour in ServiceNow Javascript.