● JavaScript Initializations are Not Hoisted

JavaScript only hoists declarations, not initializations.
below two examples are similar, But result is different.

This because only the declaration ( var y), not the initialization (=7) is hoisted to the top.
Because of hoisting, y has been declared before it is used, but because initializations are not hoisted, the value of y is undefined.

● JavaScript try and catch

● JavaScript Throws Errors

● The throw Statement

● Input Validation Example

● HTML Validation

● The finally Statement

● The Error Object

● Error Object Properties

https://www.w3schools.com/js/js_errors.asp

● Error Name Values

6 different values can be returned by the error name property.

https://www.w3schools.com/js/js_errors.asp

● Range Error

A RangeError is thrown if programmer use a number that is outside the range of legal values. 

● Reference Error

A ReferenceError is thrown if programmer use a variable that has not been declared.

● Syntax Error

A SyntaxError is thrown if programmer try to evaluate code with a syntax error.

● Type Error

A TypeError is thrown if programmer use a value that is outside the range of expected type.

● URI Error

A URI Error is thrown if programmer use illegal characters in a URI function.

● Using String  search() With a Regular Expression

● Using String replace() With String

● Regular Expression Modifiers

● Regular Expression Patterns

● Using the RegExp Object

https://www.w3schools.com/js/js_bitwise.asp

● Bitwise AND

● Bitwise OR

● JavaScript Bitwise Operations.

 JSP Bitwise operations works on 32bits signed integers.

Any number in a bitwise operation is converted into a 32 bit signed integer.

The result of a bitwise operation is converted back into a JavaSCript number.

● JavaScript Bitwise AND ( & )

Bitwise AND returns 1 only if both bits are 1.

● JavaScript Bitwise OR (|)

Bitwise OR returns 1 if one of the bits are 1.

● JavaScript Bitwise XOR ( ^ )

Bitwise XOR returns 1 if the bits are different.

● JavaScript Bitwise NOT ( ~ )

● JavaScript (Zero fill) Bitwise Left Shift (<<)

This is a zero fill left shift. One or more zero bits are pushed in from the right, and the leftmost bits fall off.

• string
• number
• boolean
• object
• function

• Object
• Date
• Array

• null
• undefined

● The typeof Operator

Programmer can use the typeof operator to find the data type of a JSP variable.

● The Data Type of typeof

The typeof operator is not a variable. It is an operator. Operators do not have any data type. But, the typeof operator always returns a string.

● The constructor Property

The constructor property returns the constructor function for all JSP variables.

● JavaScript Type Conversion

JavaScript variables can be converted to a new variable and another data types.

• By the use of a JavaScript function
• Automatically by JavaScript itself

● Converting Numbers to Strings

The global method String() can convert numbers to strings.
It can be used on any type of numbers, literals, variables, or expressions.

The number Method toString() does the same.

● Converting Strings to Numbers

The global method Number() can convert strings to numbers.
Strings containing numbers convert to numbers.
Empty strings convert to 0.
Anything else converts to NaN ( Not A Number ).

● The Unary + Operator

The unary + operator can be used to convert a variable to a number.

If the variable can not be converted, it will still become a number, but with the value NaN.

● Converting Booleans to Numbers

The global method Number() can also convert booleans to numbers.

● Automatic Type Conversion

When JavaScript tries to operate on a "wrong" data type, it will try to convert the value to a "right" type.

https://www.w3schools.com/js/js_type_conversion.asp

● Automatic String Conversion.

JavaScript automatically calls the variable's toString() function when programmer try to "output" an object or a variable.

● The Continue Statement

The continue statement breaks one iteration ( in the loop ), if a specified condition occurs, and continues with the next iteration in the loop.

● JavaScript Labels

To label JavaScript statements Programmer precede the statements with a label name and a colon.
The break and the continue statements are the only JSP statements that can "jump out of" a code block.
The continue statement ( with or without a label reference) can only be used to skip one loop iteration.
The break statement, without a label reference, can only be used to jump out of a loop or switch.
With a label reference, the break statement can be used to jump out of any code block.

● The Do/While Loop

The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

● Different Kinds of Loops

 JavaScript supports different kinds of loops.

• for - loops through a block of code a number of times
• for/in - loops through the properties of an object
• while - loops through a block of code while a specified condition is true
• do/while - also loops through a block of code while a specified condition is true

● The For Loop

 The For loop is often the tool programmer will use when he want to create a loop.

● The For/In Loop

 The JavaScript for/in statement loops through the properties of an object.

● The break keyword

When JavaScript reaches a break keyword, it breaks out of the switch block.
this will stop the execution of more code and case testing inside the block.
When a match is found, and the job is done, it's time for a break. There is no need for more testing. It is not necessary to break the last case in a switch block. The block breaks there anyway.

● The default keyword

The default keyword specifies the code to run if there is no case match.

The default case does not have to be the last case in a switch block.

● Common Code Blocks

Sometimes programmer will want different switch cases to use the same code.
In this example case 4 and 5 share the same code block, and 0 and 6 share another code block.

https://www.w3schools.com/js/js_comparisons.asp

● Logical Operators

 Logical operators are used to determine the logic between variables or values.
Given that x =6 and y =3, the table below explains the logical operators.

https://www.w3schools.com/js/js_comparisons.asp

● Conditional ( Ternary ) Operator

 JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.