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Datatype in JavaScript

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Rajat Saxena

This document discusses JavaScript data types including numbers, strings, Booleans, objects, undefined, and null. It notes that JavaScript is a dynamically typed language where variables do not need to be declared. The key data types are described, for example numbers can be integers or floats, strings are immutable sequences of characters, Booleans have two values of true or false, and objects store keyed collections of values that can be changed. The differences between null and undefined are presented as a question for an exercise.

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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
Data Types in JavaScript ● Numbers ● Strings ● Boolean ● Objects ● Undefined ● Null
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
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’
Boolean ● Represents logical entity ● Can have two values – true – false
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.
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.
Null ● Represents absence of any object value ● Operation “typeof null” yields “object”
Exercise ● What are the differences between “null” and “undefined”? ● How would you test that a variable is defined and has a non-null value?
Exercise ● What are the differences between “null” and “undefined”? ● How would you test that a variable is defined and has a non-null value?

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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?