Javascript Operators

JavaScript Operators and Expressions

• JavaScript has operators to manipulate data objects
• Operators are symbols like +, -, =, >, and <.
• Operands are the data objects that operators manipulate, such as 5 and 4 in the expression 5 + 4
• Expressions combine values to make a new value as in n = 5 + 4
• A complete statement is an expression terminated with a semicolon, such as n = 5 + 4;

Assignment Operator

• Assigns a value to a variable.
• Assignment statements evaluate the right side of the equal sign and assign the result to the variable on the left.
• The equal sign (=) is the assignment operator.

Precedence and Associativity

• Precedence determines how operators bind to operands, resolving ambiguity in expressions like 5 * 4 + 3 / -2.2
• Multiplication has higher precedence than addition, binding more tightly to its operands
• Assignment operators have low precedence
• Parentheses have the highest precedence; expressions inside them are evaluated first, starting with the innermost set in nested parentheses.
• Associativity determines the order operators evaluate their operands.
• With equal precedence, evaluation is from left to right

Example

• An example shows how precedence affects the outcome of expressions
• The expression "var x = 5 + 4 * 12 / 4" results in x = 17 due to multiplication and division having higher precedence than addition.

Types of Operators

Arithmetic Operators

• Arithmetic operators - take numerical values and return a single numerical value.
• The standard arithmetic operators are addition (+), subtraction (–), multiplication (*), and division (/).

Shortcut Assignment Operators

• Allow you to perform an arithmetic or string operation by combining an assignment operator with an arithmetic or string operator.
• For example, x = x + 1 can be written x+=1.

Autoincrement and Autodecrement Operators

• Autoincrement (++) and autodecrement (--) operators simplify code, incrementing or decrementing a variable by 1.
• There are prefix (++x or --x) and postfix (x++ or x--) forms
• In simple operations, the effect is the same i.e. x++ or x−−, ++x or --x, the effect is the same; both ++x and x++ add one to the value of x, and both -x and x- - subtract one from the value of Χ.
• ++x and x++ add one to the value of x,
• --x and x-- subtract one from the value of x

Concatenation Operator

• Use the + sign for concatenation (joining strings) and addition.
• JavaScript has manipulate strings using concatenation.

Comparison Operators

• Compare operands, uses relational and equality operators, numbers or strings
• comparison result - true or false (Boolean value).
• == is equal to
• != is not equal to
• x === y is identical to y in value and type
• x !== y is not identical to y

Logical Operators

• Combine relational operators for testing conditions.
• Evaluation proceeds from left to right, testing the Boolean value of each operand.
• && is the logical AND operator - If the expression on the left-hand side of the && evaluates to zero, null, or the empty string "", the expression is false.
• || is the logical OR operator - If the expression on the left-hand side of the || operator is evaluated as true (non-zero), the value of the expression is true, and no further checking is done.
• ! is the logical NOT operator - returns true if the expression evaluates to false and returns false if the expression evaluates to true

Conditional Operator

• The conditional operator is a ternary operator because it requires three operands - shorthand for if/else conditional statements.
• FORMAT - conditional expression ? expression : expression
• if x evaluates to true, the value of the expression becomes y, else the value of the expression becomes z

Number, String, or Boolean? Datatype Conversion

• JavaScript is a loosely typed language, so it will try and handle the data conversions for you
• There are times when you want to force a conversion of one type to another for example if you prompt a user for input, the input is set as a string, but if you want to perform calculations you want to convert it into a number first
• JavaScript provides three methods to convert the primitive data types:

String()

• Convert to String

Number()

• Convert to Number

Boolean()

• Convert to Boolean

The parseInt() Method

• This method converts a string to a number
• Starts parsing at the beginning of the string and returns all integers until it reaches a non-integer and then stops parsing

The parseFloat() Method

• This returns a floating-point number
• he decimal point is allowed in the string being parsed
• If the string being parsed does not start with a number, NaN (not a number) is returned.

The eval() Method

• The eval() method evaluates a string of JavaScript statements and evaluates the whole thing as a little program, returning the result of the execution.
• If there is no result, undefined is returned.