Data types
5 different data types can contain values: string number boolean true and false object function 3 types of objects: Object Date Array 2 data types cannot contain values: null undefined Use the typeof operator to find the data type of a JavaScript variable.
Data type conversion
JavaScript is a dynamically typed language. That means you don't have to specify the data type of a variable when you declare it.
Converting strings to numbers
In the case that a value representing a number is in memory as a string, there are methods for conversion. parseInt() parseFloat() Converting Booleans to Strings The global method String() can convert booleans to strings.