JavaScript

JavaScript

1. Values

2. Comments

   • // This is a comment
   • /*Multi line comment*/
   • Prevents execution

3. Expressions

4. Operators

   • JavaScript Arithmetic Operators
     • +
       • adds numbers
     • -
       • subtracts numbers
     • *
       • multiplies numbers
     • /
       • divides numbers
     • %
       • returns the division remainder
     • ++
       • increments numbers
     • --
       • decrements numbers
     • Numbers are called operands
     • The operation (to be performed between the two operands) is defined by an operator
     • Arithmetic operators perform arithmetic on numbers (literals or variables)
   • JavaScript Assignment Operators
     • Assignment operators assign values to JavaScript variables
     • =
     • +=
     • -=
     • *=
     • /=
     • %=
     • <<=
     • >>=
     • >>>=
     • &=
     • ^=
     • |=
   • JavaScript String Operators
     • txt3 = txt1 + " " + txt2;
     • txt1 = "What a very "; txt1 += "nice day";
   • JavaScript Comparison Operators
     • ==
       • equal to
     • ===
       • equal value and equal type
     • !=
       • not equal
     • !===
       • not equal value or not equal type
     • >
       • greater than
     • <
       • less than
     • >=
       • greater than or equal to
     • <=
       • less than or equal to
   • JavaScript Logical Operators
     • &&
       • and
     • ||
       • or
     • !
       • not
   • JavaScript Type Operators
     • typeof
       • Returns the type of a variable
     • instanceof
       • Returns true if an object is an instance of an object type
   • JavaScript Bitwise Operators
     • &
     • |
     • ~
     • ^
     • <<
     • >>
     • >>>
   • Conditional (Ternary) Operator
     • JavaScript also contains a conditional operator that assigns a value to a variable based on some condition
     • variablename = (condition) ? value1:value2

5. Keywords

   • break
     • Terminates a switch or a loop
   • continue
     • Jumps out of a loop and starts at the top
   • debugger
     • Stops the execution of JavaScript, and calls (if available) the debugging function
   • do .. while
     • Executes a block of statements, and repeats the block, while a condition is true
   • for
     • Marks a block of statements to be executed, as long as a condition is true
   • function
     • Declares a function
   • if ... else
     • Marks a block of statements to be executed, depending on a condition
   • return
     • Exits a function
   • switch
     • Marks a block of statements to be executed, depending on different cases
   • try ... catch
     • Implements error handling to a block of statements
   • var
     • Declares a variable