#05 - Differences between
2016-01-05 by @loverajoel
undefinedmeans a variable has not been declared, or has been declared but has not yet been assigned a value
nullis an assignment value that means “no value”
null. It is used by programmers to indicate that a
varhas no value.
undefinedis not valid in JSON while
nulltypeof is an
Both are primitives
Both are falsy (
Boolean(undefined) // false,
Boolean(null) // false)
You can know if a variable is undefined
typeof variable === "undefined"
The equality operator considers them equal, but the identity doesn’t
null == undefined // true null === undefined // false