Commenting & Variables

What is a comment?

A comment is a way to leave notes for anyone who reads the code.

In JavaScript, the pattern // is reserved to create a single line of code that will be converted to a comment.

The JavaScript compiler will always ignore a line of comment when it sees the pattern of // in the beginning of the line.

How does a JavaScript program execute its code?

The JavaScript compiler which translate our written instruction to a language that a computer can understand will translate the JavaScript code in order from top to bottom.

The code will then execute its instruction from top to bottom.

What is a variable?

Variables are named placeholders that allow a programmer to attach important data that a program would need to an easy label that can be used to reference later.

Variable Naming Convention

1. start with lowercase letters

2. labels that have multiple words are either camelCased or use under_scores

3. labels cannot be the same as the built-in keywords in Java

4. labels should not be ambiguous let a = "Park"; is less descriptive than let last_name = "Park";

Our Program Above

// Learning comments and variable
let greeting = "Hi, how are you?";

console.log(greeting);

1. Comment:

   // Learning comments and variable

   • This is a single-line comment. Comments are used to leave notes or explanations in your code. They are ignored by the JavaScript engine and do not affect the execution of the program.

2. Variable Declaration and Initialization:

   let greeting = "Hi, how are you?";

   • let is a keyword used to declare a variable. In this case, the variable is named greeting.

   • The variable greeting is assigned the string value "Hi, how are you?".

3. Output to Console:

   console.log(greeting);

   • console.log() is a function that prints the value of greeting to the console.

   • When this line is executed, it will output: Hi, how are you?

So, when you run this program, it will display the message "Hi, how are you?" in the console.