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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 :
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).
A floating number has the following parts.
The exponent part is an "e" or "E" followed by an integer, which can be signed (preceded by "+" or "-").
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
JavaScript has the following types of 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. |
| Shorthand | Expression | Description |
|---|---|---|
| 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. |
| a<<=b | a = a<<b | Performs a left shift and assigns the result to the first operand. |
| a>>=b | a = a>>b | 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. |
| Operator | Comparisons |
Description |
|---|---|---|
| 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. |
| Operator | Comparisons |
Description |
|---|---|---|
| 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 (<) | x<y | Returns true if the left operand is less than the right operand. |
| Less than or equal (<=) | x<=y | Returns true if the left operand is less than or equal to the right operand. |
| Operator | Usage | Description |
|---|---|---|
| Bitwise AND | a & b | Returns a one in each bit position if bits of both left and right operands are ones. |
| Bitwise OR | a | b | Returns a one in each bit if bits of either left or right operand is one. |
| Bitwise XOR | a ^ b | Returns a one in a bit position if bits of one but not both left and right operand are one. |
| Bitwise NOT | ~ a | Flips the bits of its operand. |
| Operator | Usage | Description |
|---|---|---|
| Left shift | a << b | Shifts a in binary representation b bits to the left, shifting in zeros from the right. |
| Sign-propagating right shift | a >> b | Shifts a in binary representation b bits to the right, discarding bits shifted off. |
| Zero-fill right shift | a >>> b | Shifts a in binary representation b bits to the right, discarding bits shifted off, and shifting in zeros from the left. |
| Operator | Usage | Description |
|---|---|---|
| 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. |
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.
JavaScript has the following special operators.
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]);
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 provides an identifier for a statement that lets you refer to it using a break or continue statement.
JS BinIn JavaScript all values except the primitive types of JavaScript (true, false, numbers, strings, null and undefined) are objects.
Here objects contain -> propertyName: propertyValue pairs.
JavaScript has the following predefined objects.
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