detect "null"

[parabuh]

@ulrik you can use shorthand

if (!var) {
}

[d.healey]

@parabuh That won't tell you is the variable is null

[ustk]

@d-healey Hmmm... I just discovered that a value of 0 == undefined Back to school for me!

[ulrik]

@parabuh that will not work

[d.healey]

@ustk I never use var == undefined I always use isDefined(var)

I just noticed this guy commented on my video (I think I might re-record that one)

[ulrik]

@d-healey

if I declare a variable like this

const t = null;

First I'll get

Console.print(t);
API call with undefined parameter 0

Console.print(t == void);
result: 1

Console.print(t == undefined);
result: 1

Console.print(t == null);
result: 1

Console.print(t === void);
result: 0

Console.print(t === undefined);
result: 0

Console.print(t === null);
result: 1

but my variable show up as null, and if I use

Console.print(myvariable === null);
result: 0

Are there different kind of "null"??

[d.healey]

@ulrik Are you sure your variable is null?

[ulrik]

@d-healey that's what it's saying if I Console.print it
my var is inside an array and if trace log it will say something like this:

Interface: [
  3,
  null
]

[d.healey]

@ulrik I think you need to give us an example we can test.

This works for me:

const a = [3, null];

Console.print(a[1] === null);

So you must be doing something different.

[ulrik]

@ulrik Ok, I Console.print each member of the array and got this instead:

Interface: inf

so if trace logged it show up as "null" and if logged independently it show up as "inf"

[ulrik]

@ulrik @d-healey so what does "inf" stand for, infinite?

[d.healey]

@ulrik No idea. I'd recommend you try to always populate your variables yourself so you know what it contains.

[Christoph Hart]

Yes, inf is infinite:

Console.print(1.0 / 0.0)

But the question is: how did you get null in the first place? I honestly didn't know that existed, we've got undefined for a uninitialized variable, void for a invalid array or object field and inf and nan for illegal number values.

var x = 1 / 0.0;
x = 0.0 * x;

var a = [1];
var n;

Console.print(typeof(a[9])); // => void
Console.print(typeof(b)); // => undefined
Console.print(typeof(1.0 / 0.0)); // => number
Console.print(typeof(n)); // => undefined
Console.print(x); // => nan

[ulrik]

@Christoph-Hart ok thanks!

As I said here:

@ulrik Ok, I Console.print each member of the array and got this instead:

Interface: inf

so if trace logged it show up as "null" and if logged independently it show up as "inf"

It seems the

Console.print(trace(array))

is not showing correct information?

[Christoph Hart]

@ulrik I just skimmed through the JUCE codebase and the only time where null is used is when you convert a JSON object with a void field to a string (which would be the case if you do something like Console.print(trace(array) command). I guess that's just for compatibility reasons with the JSON standard and it is still being typed internally as void. I can't say why it is behaving like that with an inf number though, as this is clearly a number type and should be treated as such (eg. isDefined(1.0/0.0) returns true).

However I got this output:

so apparently assigning void to a field is the same as assigning undefined (which I thought were two different things), however the isDefined() check works correctly on all of them.

BTW, using inf as literal is not protected, so you can do stuff like:

var inf = 90;
Console.print(inf);

[ustk]

@Christoph-Hart Is it normal that a[2] set to null is throwing undefined ? It's weird to me because it is actually defined as null...

EDIT: I think I have my answer...

What is the difference between null and undefined in JavaScript?

What is the difference between null and undefined in JavaScript?

Stack Overflow (stackoverflow.com)

console.log(null === undefined) // false (not the same type)
console.log(null == undefined) // true (but the "same value")

[ulrik]

@ustk