JavaScript_course

Expressions & Operators

Expressions

An expression evaluates into (results) in a single value. Broadly speaking there are two types of expressions.

• EXPRESSIONS THAT JUST ASSIGN A VALUE TO A VARIABLE.

  // var or let
  var color = "beige";
  

• EXPRESSIONS THAT USE TWO OR MORE VALUES TO RETURN A SINGLE VALUE.

  // var or let
  var area = 3 * 2;
  

Operations

Expressions rely on things called operators, they allow programmers to create a single value from one or more values.

Operation types are:

1. Assignment operators.

   var color = "beige";
   

2. Arithmetic operators.

   var area = 3 * 2;
   

3. String operators.

   var greeting = "Hi " + "Molly";
   

4. Comparison operators.

   var buy = 3 > 5;
   

5. Logical operators.

   var buy = 5 > 3 && 2 < 4;
   

point 4 and 5 covered in chapter 4

Arithmetic operators

JavaScript contains the following mathematical operators, which you can use with numbers.

Name	Operation	Purpose & notes	Example	result
ADDITION	+	Adds one value to another	10 + 5	15
SUBTRACTION	-	Subtracts one value from another	10 - 5	5
DIVISION	/	Divides two values	10 / 2	2
MULTIPLICATION	*	Multiplies t wo values using an asterisk not x	10 * 5	50
INCREMENT	++	Adds one to the current number	i = 10; i++;	11
DECREMENT	–	Subtracts one from the current number	i = 10; i–;	9
MODULUS	%	Divides two values and returns the remainder	10 % 3	1

Order of execution

We have to take care of those rules with arithmetic operations:

1. Multiplication and division are performed before addition or subtraction.

       total 2 + 4 * 10; // Result ??
   

2. Parentheses are first calculated even before multiplications or division.

   total = (2 + 4) * 10; // result ??
   

// Ahmed write them c02/js/arithmetic-operator Program

String operator

There is just one string operator: the + symbol. It is used to join the strings on either side of it.

ES5

var firstName = "Ivy ";
var lastName = " Stone";
var fullName = firstName + lastName; // Ivy Stone

ES6

let firstName = "Ivy ";
let lastName = " Stone";
let fullName = `${firstName} ${lastName}`;

Mixing number and strings together

When you place quotes around a number, it is a string (not a numeric data type), and you cannot perform addition operations on strings

var costl = "7";
var cost2 = "9 ";
var total = costl + cost2; // '79' as string not a number

If you try to add a numeric data type to a string, then the number becomes part of the string.

var number = 12;
var street = "Ivy Road";
var add = number + street; // '12Ivy Road'

If you try to use any of the other arithmetic operators on a string, then the value that results is usually a value called NaN means not a number.

var score = "seven ";
var score2 = " nine";
var total = score * score2; // NaN

// Ahmed write them c02/js/string-operator Program

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References and Terms:

:information_source: Read more about Camel case :information_source: Read more about Snake case