An expression is any valid JavaScript code that resolves to a value.

This means, it's any JavaScript code that has an end result, for example:

• 1 + 2
• typeof(4)
• new Date()
• 2 * 4

And the list goes on...

Every one of these expressions, resolves to a value, for example:

• 1 + 2 resolve to the number 3
• typeof(4) resolves to the primitive data type number
• new Date() resolves to a date object
• 2 * 4 resolves to the number 8