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reading-notes

Code 102, Intro to Software Development

Class 07 - Reading Notes

Programming with JavaScript

Control Flow

Control flow: the order in which the computer executes statements in a script. Generally, code executes from top to bottom unless the code encounters a structure that changes the control flow, such as a conditional or a loop.

Reminder: Conditional Structures include if…else

JavaScript Functions

Summarized from W3Schools

A function is a block of code designed to perform a particular task. A JS function is executed when “something” calls it.

For example:

function myFunction(p1, p2) { return p1 * p2; // The function returns the product of p1 and p2 }

JavaScript Function Syntax

JS functions are defined with the function keyword, followed by a name (you choose the name), followed by parentheses ().

Function names can contain letters, digits, underscores, and $ signs. Parentheses may include parameter names separated by commas: (parameter1,parameter2). The code to be executed by the function is placed inside curly brackets.

Function arguments are the values received by the function when it is invoked.

In other programming languages, function is much the same as procedure or subroutine

Function Invocation

The code inside the function will execute when “something” invokes the function:

When an event occurs (user clicks a button)

When it is invoked from JS code

Automatically (self-invoked)

Function Return

When JS reaches a return statement, the function will stop executing. If the function was invoked from a statement, JS will “return” to execute the code after the invoking statement. Functions often compute a return value. The return value is “returned” back to the caller.

let x = myFunction(4, 3); // Function is called, return value will end up in x

function myFunction(a, b) { return a * b; // Function returns the product of a and b }

The `()` Operator

Accessing a function without () will return the function definition (object) instead of the function result.

Local Variables

Variables declared within a JS function become local to the function, and can only be accessed from within the function. Since local variables are only recognized inside their functions, variables with the same name can be used in different functions. They are created when a function starts, and deleted when the function is complete.