Comments

Comments are notes you write inside your code. JavaScript completely ignores them - they exist only to help humans understand the code.

To write a single-line comment, use //. Everything after // until the end of the line is ignored:

// This is a comment
console.log("Hello!")

A comment can also be written at the end of a line, after the code:

console.log("Hello!") // This prints Hello!

For comments that span several lines, use /* to start and */ to end:

/* This is a multi-line comment.
   JavaScript ignores all of it. */
console.log("Welcome!")

Comments can also temporarily disable a line of code without deleting it:

// console.log("This line will NOT run")
console.log("This line will run")

Note: Every multi-line comment that starts with /* must be closed with */, otherwise JavaScript reports a syntax error and none of the code runs, not even the lines before the comment.