The Grammar Hammer

About let You use the let keyword to tell JavaScript you are making a new variable. Once the variable is created, you do not need to use let on that variable again.

In some older references, you will see var used instead of let. You should use let instead. Later we will see why this is a better way of doing things.

Variables are just symbols you store data under. The rules for variable names are simple.

• The first character must be alpha or an _
• Subsequent characters can be alphanumeric or _

You will often see camel notation in JavaScript, which sets off words with capital letters. Example: numberOfItems. Your python programming peers use snake notation that looks like this: number_of_items. Use variable names that are evocative of their roles.

Semicolons A semicolon in JavaScript is like a period in English. It means a sentence has come to a full stop. All of the statements you learn about in this initial part of the course are called worker statements and they are complete senetences.

Therefore, they should end with a semicolon.

Making and Running JS Programs.

console.log This function prints stuff to the console. Let's do some exercises with it. Make this file hello.js.

//Program helloWorld.js
console.log("Hello, World");

To run it do the following.

1. Open empty.html in your browser.
2. Copy the program.
3. Paste the program into the console.
4. Hit the enter key.

Often you will want to refresh the browser between runs, especially if you get error messages.