Free JavaScript course. Sign Up for tracking progress →

JavaScript: Operators

Before we move on, let's take a look at the basic terminology. Operation signs such as + are called operators. They perform operations on certain values (operands). Operators are usually represented by one or more symbols, but occasionally, they can be represented by a word. Most of the operators are identical to those you'll have seen in math class.

console.log(8 + 2);

Here the + is an addition operator, 8 and 2 are operands.

The addition operation has two operands, positioned to the left and right of the operator +. Operations with two operands are called binary operations. If at least one operand is missing, for example, 3 + ; then the program will throw out a syntax error.

Besides binary operations (not operators) there are unary operations (with one operand) and even ternary (with three operands)! Moreover, operators may look the same but denote different operations.

  console.log(-3); // => -3

In the example above, the unary operation applies to 3. An interpreter will read it as follows: the minus operator tells it to take the number 3 and find the opposite, which is -3.

You might be a bit confused since -3 is both a number and an operator with an operand, but that's simply how programming languages work.


Write a program that calculates and prints the difference between 6 and -81.

The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

  • Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

I've read the lessons but nothing is clear 🙄

It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.

By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.



  • Arithmetic operations are addition, subtraction, multiplication and division.

  • Unary operation is an operation with only one operand. For example, -3 is an unary operation to get the number which is opposite to 3.

  • Binary operation is an operation involving two operands. For example, 3 + 9.

If you got stuck and don't know what to do, you can ask a question in our community