Truth or lies JS edition

Question 1

Does an empty object evaluate to false?

Answer 1

No it does not, objects even empty ones evaluate to true!

if ( { } ) {
alert( “ This will run! “ );
}

Question 2

What is a falsy value ?

Answer 2

Afalsyvalue is a value that is considered false when encountered in aBooleancontext

Question 3

How does JavaScript create falsy and truthy values? In what contexts does JavaScript need to do this ?

Answer 3

JavaScript uses type conversion to coerce any value to a Boolean in contexts that require it, such as conditionals and loops.

Question 4

There are 9 falsy values listed on MDN what are they ?

Answer 4

1. The keywordfalse
2. TheNumberzero (so, also0.0, etc., and0x0).
3. The Number negative zero (so, also -0.0, etc., and -0x0).
4. 0n
   The BigInt zero (so, also 0x0n). Note that there is no BigInt negative zero — the negation of 0n is 0n.
5. ””,’’,``Emptystringvalue.
6. null — the absence of any value.
7. NaN — not a number.
8. undefined — the primitive value.

9.document.all
Objects are falsy if and only if they have the [[IsHTMLDDA]] internal slot. That slot only exists in document.all and cannot be set using JavaScript.

Question 5

What values in JavaScript are truthy ?

Answer 5

All values aretruthyexcept
false,0,-0,0n,”“,null,undefined, andNaN.

Also document.all