How to test if a variable is a Moment.js object?

Question

My application has an HTML form with some inputs populated from the backend and other inputs being entered by the user (in a time input). An onChange function runs through each input when the user changes a value.

The inputs populated from the backend are converted to moment objects, the user-entered dates are mere strings. This means the onChange function encounters some moment objects, and some strings. I need to know which inputs are moment objects and which aren't.

What's the recommended method for testing if a variable is a moment object?

I've noticed moment objects have a _isAMomentObject property but I'm wondering if there's another way to test if a variable is a moment object.

Another option I've tried is calling moment on the variable regardless. This converts the string variables to moment objects and doesn't seem to effect existing moment objects.

Answer 1

Moment has an isMoment method for just such a purpose. It is not particularly easy to find in the docs unless you know what to look for.

It first checks instanceof and then failing that (for instance in certain subclassing or cross-realm situations) it will test for the _isAMomentObject property.

Answer 2

You can check if it is an instanceof moment:

moment() instanceof moment; // true

Answer 3

moment() instanceof moment;

will always be true, because if you have

• moment(undefined) instanceof moment
• moment("hello") instanceof moment

you are always creating a moment object. So the only way is to check like this

• moment(property).isValid()