Basics: Operators and expressions

Operators allow you to get two simple expressions and combine them to form a more complex expression.

But first.. what is an expression? An expression is a single unit of JavaScript code that the JavaScript engine can evaluate, and return a value.

An expression can be a literal, like a string or a number.

It can also be an identifier that points to a variable.

Like these:

age //where 'age' is the name of a variable
{} //an empty object

We also have other kinds of expressions.

Arithmetic expressions are expressions that take a variable and an operator (more on operators soon), and result in a number:

1 / 2
i -= 2
i * 2

String expressions are expressions that result in a string:

'A ' + 'string'

Logical expressions make use of logical operators and resolve to a boolean value:

a && b
a || b

More advanced expressions involve objects, functions, and arrays, and I’ll introduce them later.

Lessons in this unit:

0: Introduction
1: Literals, identifiers and variables
2: Comments
3: The difference between let, const and var
4: Types
5: ▶︎ Operators and expressions
6: Let's start with arithmetic operators
7: The assignment operator
8: Operators precedence
9: Strings
10: Numbers
11: Semicolons, white space and sensitivity