JavaScript Comments and Conditionals

Charles Russell

Bennu Bird Media

Note Taking

● Detectives journal● Fire Log● Sketch books

● In programs we use comments

Comments are for people not machines

● Notes to others and ourselves describing our thinking.

● Often used to outline the program with pseudo code.

● Establish proprietary information like authorship copyright and other

● Documentation

Comments in JavaScript

● Single line comment //● From where the comment begins to end of line

● Multi-line comment /* */● Begins with /* and continues to be ignored no matter

how many lines until */● Documentation comment /** */

● Used by documentation tools like Scriptdoc or Doxygen to document code in the code document and extract to either a sepeate document of web page.

Branching out

● It is very common to want to decide one of two paths for a program to take● Statements that choose between multiple courses of action are called conditional

statemens● If statements provide that branch

● if (condition ) doSomething() else doSomethingElse()

if (boolean) {

statement1;

statement2;

}else{

// This code block executes if falsey

…

}

Multibranch Selection

● If great for when you have only two possible paths● What if you have many paths

● else if to the rescue

if (condition) {

doSomething

} else if ( condition) {

doAnotherThing

} else{

doSomethingElse

Switch JavaScript's Manifold

● Switch is another way to branch into one of many paths● Two other keywords needed for this statement

– case: this is the conditional– break Breaks out of the switch

● Optional default keyword– This part of the switch is executed if no other condition is

met

Switch the syntax

switch (a) {

case value:

statements

break;

case value2:

statements

break;

default:

statements

}

Summary

● Comments allow to keep notes and document your code● There are single line and multiline comment types

● A special multiline comment can aid in documentation● Conditional statements allow branching to alter operational

flow.● { } define code blocks (and somethings we will get to soon)● If ( conditional expression) {..}else if {..} else{..}

– Else optional● Switch is used for selecting from multiple code blocks

– case and break needed with optional default

Next: Iterations