Datatype in JavaScript
- 1. Couple-O-Points ● JavaScript is a “loosely typed” or “dynamic” language. ● So we don’t have to declare type of a variable ahead of time. ● You can check the type of any variable using ‘typeof’ operator
- 2. Data Types in JavaScript ● Numbers ● Strings ● Boolean ● Objects ● Undefined ● Null
- 3. Numbers ● JavaScript has single number type ● It is represented as 64-bit floating point ● No separate type of Integer (like Java etc.) ● 2e3 means 2000 i.e 2 multiplied by 10 raised to the power after ‘e’ symbol. ● In addition, Number type also has three symbolic values – Infinity – -Infinity – NaN
- 4. Strings ● Set of “elements” of 16-bit unsigned integer values. ● Each element in the String occupies a position in String ● Strings are immutable ● Strings have methods, useful ones, like: – length() – ToUpperCase() ● New strings can be made using concatenation (‘+’) operator. Interesting case: – ‘r’ + ‘a’ + ‘j’ === ‘raj’
- 5. Boolean ● Represents logical entity ● Can have two values – true – false
- 6. Objects ● Objects are collection of properties ● Properties can be removed and added, after object has been created ● Object is a mapping between keys and values – A key value is either a symbol or string value – Values can be of any type i.e Number, Boolean, Object etc ● Objects are mutable.
- 7. Undefined ● It’s a property of global object ● A variable that has not been assigned a value is of type undefined. ● A function returns undefined if a value was not returned.
- 8. Null ● Represents absence of any object value ● Operation “typeof null” yields “object”
- 9. Exercise ● What are the differences between “null” and “undefined”? ● How would you test that a variable is defined and has a non-null value?
- 10. Exercise ● What are the differences between “null” and “undefined”? ● How would you test that a variable is defined and has a non-null value?