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Showing content from https://developer.mozilla.org/en-US/docs/Glossary/Falsy below:

Falsy - Glossary | MDN

Falsy

A falsy (sometimes written falsey) value is a value that is considered false when encountered in a Boolean context.

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

The following table provides a complete list of JavaScript falsy values:

Value Type Description null Null The keyword null â the absence of any value. undefined Undefined undefined â the primitive value. false Boolean The keyword false. NaN Number NaN â not a number. 0 Number The Number zero, also including 0.0, 0x0, etc. -0 Number The Number negative zero, also including -0.0, -0x0, etc. 0n BigInt The BigInt zero, also including 0x0n, etc. Note that there is no BigInt negative zero â the negation of 0n is 0n. "" String Empty string value, also including '' and ``. document.all Object The only falsy object in JavaScript is the built-in document.all.

The values null and undefined are also nullish.

Examples

Examples of falsy values in JavaScript (which are coerced to false in Boolean contexts, and thus bypass the if block):

if (false) {
  // Not reachable
}

if (null) {
  // Not reachable
}

if (undefined) {
  // Not reachable
}

if (0) {
  // Not reachable
}

if (-0) {
  // Not reachable
}

if (0n) {
  // Not reachable
}

if (NaN) {
  // Not reachable
}

if ("") {
  // Not reachable
}

The logical AND operator, &&

If the first object is falsy, it returns that object:

console.log(false && "dog");
// âª false

console.log(0 && "dog");
// âª 0