Created by w3resource.com / @w3resource JavaScript recognizes the following types of primitive values. A JavaScript variable must start with a letter [A-Z, a-z], underscore [_], or dollar sign [$], subsequent characters can also be digits [0-9]. - Declaring variables - Use literals to represent values in JavaScript which are fixed values, not variables. The Boolean type has two literal values :Course
Instructions
JavaScript, The Language of the Web
JAVASCRIPT IS EVERYWHERE
Write once, run everywhere
JAVASCRIPT LANGUAGE
JAVASCRIPT BASICS
Hello world
JS BinValues
VARIABLES
ALWAYS DECLARE YOUR VARIABLES WITH VAR!!!
Literals & Expressions
Boolean
literals
- true
- false
Integers
Integers can be expressed in decimal [base 10], hexadecimal [base 16], and octal [base 8]. An integer must have at least one digit [0-9].
- No comma or blanks are allowed within an integer.
- It does not contain any fractional part.
- It can be either positive or negative, if no sign precedes it is assumed to be positive.
Floating-point literals
A floating number has the following parts.
- A decimal integer.
- A decimal point ['.'].
- A fraction.
- An exponent.
The exponent part is an "e" or "E" followed by an integer, which can be signed [preceded by "+" or "-"].
Expressions
An expression is any valid unit of code that resolves to a value. Conceptually, there are two types of expressions: those that assign a value to a variable [a = 12] and those that simply have a value [5-3].
Expression categories
- Arithmetic: evaluates to a number, for example 120.230.
- String: evaluates to a character string, for example, "w3r" or "2001".
- Logical: evaluates to true or false.
- Object: evaluates to an object.
Operators
JavaScript has the following types of operators.
- Assignment operators
- Comparison operators
- Arithmetic operators
- Bitwise operators
- Logical operators
- String operators
- Special operators
Arithmetic operators
addition [+], subtraction [-], multiplication [*], and division [/]. In addition, JavaScript provides the following arithmetic operators.
% [Modulus] | Returns the integer remainder of dividing the two operands. | 16 % 5 returns 1. |
++ [Increment] | Unary operator. Adds one to its operand. | If x is 3, then ++x returns 4, whereas x++ returns 3. |
-- [Decrement] | Unary operator. | If x is 3, then --x returns 2, whereas x-- returns 3. |
- [Unary negation] | Unary operator. Returns the negation of its operand. | If x is 3, then -x returns -3. |
Assignment operators [1/2]
a +=b | a = a + b | Adds 2 numbers and assigns the result to the first. |
a -= b | a = a - b | Subtracts 2 numbers and assigns the result to the first. |
a *= b | a = a*b | Multiplies 2 numbers and assigns the result to the first. |
a /=b | a = a/b | Divides 2 numbers and assigns the result to the first. |
a %= b | a = a%b | Computes the modulus of 2 numbers and assigns the result to the first. |
Assignment operators [2/2]
ab | Performs a sign-propagating right shift and assigns the result to the first operand. | |
a>>>=b | a = a>>>b | Performs a zero-fill right shift and assigns the result to the first operand. |
a&= b | a = a&b | Performs a bitwise AND and assigns the result to the first operand. |
a^= b | a = a^b | Performs a bitwise XOR and assigns the result to the first operand. |
a |=b | a = a|b | Performs a bitwise OR and assigns the result to the first operand. |
Comparison Operators[1/2]
Equal [==] | x == y | Returns true if the operands are equal. |
Strict equal [===] | x === y | Returns true if the operands are equal and of the same type. |
Not equal [!=] | x != y | Returns true if the operands are not equal. |
Strict not equal [!==] | x !== y | Returns true if the operands are not equal and/or not of the same type. |
Comparison Operators[2/2]
Greater than [>] | x>y | Returns true if the left operand is greater than the right operand. |
Greater than or equal [>=] | x>=y | Returns true if the left operand is greater than or equal to the right operand. |
Less than [ b | Shifts a in binary representation b bits to the right, discarding bits shifted off, and shifting in zeros from the left. |
Logical Operators
Logical AND && | a && b | is true if both a and b are true. |
Logical OR || | a || b | is true if either a or b is true. |
Logical NOT ! | !a | is true if a is not true. |
String Operators
When working with JavaScript strings sometimes you need to join two or more strings together in to a single string. Joining multiple strings together is known as concatenation.
The concatenation operator [+] concatenates two or more string values together and return another string which is the union of the two operand strings.
Special Operators
JavaScript has the following special operators.
- Comma operator
- new operators
- delete operators
- in operators
- instanceof operators
- this operators
- typeof operators
- void operators
new Operator
The new operator is used to create an instance of a user-defined object type or of one of the predefined object types Array, Boolean, Date, Function, Image, Number, Object, Option, RegExp, or String.
Syntax : var objectName = new objectType[[param1, param2, ..., paramN]];
this Operator
The this operator is used to refer the current object. In general, this refers to the calling object in a method.
Syntax : this["propertyName"]Label statement
Label statement provides an identifier for a statement that lets you refer to it using a break or continue statement.
JS BinJavaScript Objects
In JavaScript all values except the primitive types of JavaScript [true, false, numbers, strings, null and undefined] are objects.
Here objects contain -> propertyName: propertyValue pairs.
Predefined Core Objects
JavaScript has the following predefined objects.
- Array Object
- Boolean Object
- Date Object
- Function Object
- Math Object
- Number Object
- RegExp Object
- String Object
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