Javascript-5-Javascript as a language II -Operators / isNAN() / Comparison

JavaScript Operators

• arithmetic operators( + - *  / % ++ -- ) : 
• Example: (5+6)*10

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• assignment operators ( = ). . (=) is an "assignment" operator, not an "equal to" operator.: 
• Example: var x;x = 6;. The "equal to" operator is written like == in JavaScript. Other assignment operators are : (+=  -=  *=  /=  %=)

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Note:

Comparison and Logical operators are used to test for true or false.

• Comparison operators:  used in logical statements to determine equality or difference between variables or values. Lets say, x=5
• == (equals to value).  
• x==8; returns false on execution.
• x==5; returns true on execution.
• x=="5"; returns true on execution.<===
• === (equals to value and equal to type).
• x===5; returns true on execution.
• x==="5"; returns false on execution.<===
• != (not equals to value).
• x!=8; returns true on execution.
• !== (not equals value or type).
• x!==5; returns false on execution.
• x!=="5"; returns true on execution.
• x!==8; returns true on execution.
• < (lessthan). Example: x<8; returns true on execution.
• > (greaterthan). Example: x>8; returns false on execution.
• <= (lessthan or equal to). Example: x<=8; returns true on execution.
• >=(greaterthan or equal to). Example: x>=8; returns false on execution.

More Examples:

Notes: 

* When comparing a string with a number, JavaScript will convert the string to a number when doing the comparison. 

* An empty string converts to 0. 

* A non-numeric string converts to NaN which is always false.

* When comparing two strings, "2" will be greater than "12", since (alphabetically) 1 is less than 2.

* when an integer is compared to a NAN(example:  "john" or "diane" ). the expressions always results in false. hence, 2<"John" (or) 2>"John" (or) 2=="John", all returns false.

isNAN() : checks if a given variable is a number

Example:

age = Number(age);
if (isNaN(age)) {
    voteable = "Error in input";
} else {
    voteable = (age < 18) ? "Too young" : "Old enough";
}

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• Logical operators ( &&  ||  ! ). .used to determine the logic between variables or values.: Example: if x = 6 and y = 3
• (x < 10 && y > 1) is true
• (x == 5 || y == 5) is false
• !(x == y) is true

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• Ternary Operator(  ?  :  ). 
• Example: var voteable = (age < 18) ? "Too young":"Old enough";

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• Unary operator:
• can be used to convert a variable to a number:
• var y = "5";// y is a string
• var x = + y;// x is a number
• If the variable cannot be converted, it will still become a number, but with the value NaN (Not a number):
• var y = "John";// y is a string
• var x = + y;// x is a number (NaN)

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• Bitwise operators ( = ). . (=) is an "assignment" operator, not an "equal to" operator.: Example
• link to bitwise operations

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