总结:
There are 7 basic types in JavaScript.
number
for numbers of any kind: integer or floating-point.string
for strings. A string may have one or more characters, there’s no separate single-character type.boolean
fortrue
/false
.null
for unknown values – a standalone type that has a single valuenull
.undefined
for unassigned values – a standalone type that has a single valueundefined
.object
for more complex data structures.symbol
for unique identifiers.
The typeof
operator allows us to see which type is stored in a variable.
- Two forms:
typeof x
ortypeof(x)
. - Returns a string with the name of the type, like
"string"
. - For
null
returns"object"
– this is an error in the language, it’s not actually an object