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Programming with JavaScript

Resources:

Expressions and Operators

Operator Types

JavaScript Operators

  • Assignment operators - assigns value to the left based on value to the right of the operator
  • Comparison operators - compares two values and returns logical value (ex. true or false)
  • Arithmetic operators - modifies two values based on the action performed (+, -, *, /, etc)
  • Bitwise operators - treats inputs as 32 bits (0's and 1's)
  • Logical operators - typically used with Boolean value sand return a Boolean value
  • String operators - concatenation (+ when used with a string)
  • Conditional (ternary) operator - takes three inputs and results in either va11 or va12 based on whether the condition is true or false
  • Comma operator - evaluates both inputs and returns the last one
  • Unary operators - delete, this deletes an objects property
  • Relational operators - compares the inputs and returns a boolean (in)

Expression Types:

  • Arithmetic: results in a number
  • String: results in a character string
  • Logical: results in true or false
  • Primary expressions: Basic keywords and general expressions in JavaScript.
  • Left-hand-side expressions: Left values are the destination of an assignment.

Functions

JavaScript Functions

Function Declarations are intiated by using the function declaration keyword followed by the name of the function parentheses () enclosing a list of parameters, and curly braces {} capturing the JavaScript statements that define the function (code to be executed). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).

Note: Inside the function, the arguments (the parameters) behave as local variables.

function double(num) {
    return num + num;
}

Calling a function:

double(5);

returns 10

The only way to get data store in a variable declared in a function is to return that variable at the end of the function.

Variables defined in the function are ONLY available in the function.

Control Flow

Control flow is the order in which the computer executes statements in a script. This order is run from first to last line, unless there is a structure that changes the flow.

Conditionals and Loops are a way to change the flow structure.

Control flow means that when you read a script, you must not only read from start to finish but also look at program structure and how it affects order of execution.