JavaScript: Value return
Functions in JavaScript become really useful when they start to return data rather than print it. It allows them to be used for further computations. Check out this example:
const message = greetHexlet();
console.log(message);
We assign a function output to the variable message. In order to make this code work, the function must use the return instruction inside itself:
const greetHexlet = () => {
const message = 'Hello, Hexlet!';
return message;
};
return is a special statement that takes an expression written after it and sends it back to the code where the function was called. The function won't be executed beyond there, any code after return won't be carried out:
const greetHexlet = () => {
const message = 'Hello, Hexlet!';
return message;
console.log('I will never execute');
};
You don't necessarily need to use a variable to return. Since return works with expressions, almost anything can follow it. Here we should keep to the principles of code readability:
const greetHexlet = () => {
return 'Hello, Hexlet!';
};
An example of a computation:
const doubleFive = () => {
return 5 + 5;
};
But even if there is no return statement inside the function, it will still return something. By default, any function will return undefined. For example, the console.log() function prints text, but returns nothing. In this case, it returns undefined.
const result = console.log('You can put any text here');
console.log(result); // => undefined
// Or even easier, without creating an intermediate variable
console.log(console.log('Wow')); // => undefined
Why is this behavior needed? A function call is an expression, and an expression should always return a result, otherwise, there would constantly be errors in the code in places where there is no data to return.
Self-check. What will this code print?
// Definition
const run = () => {
return 5;
return 10;
}
// Usage
run(); // => ?
https://replit.com/@hexlet/js-basics-functions-return
Instructions
Write a function sayHurrayThreeTimes(), that returns a string 'hurray! hurray! hurray!'.
const hurray = sayHurrayThreeTimes();
console.log(hurray); // => hurray! hurray! hurray!
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.
Your exercise will be checked with these tests:
1// @ts-check
2
3import { test, expect } from '@jest/globals';
4import f from './index.js';
5
6test('test', () => {
7 expect(f()).toBe('hurray! hurray! hurray!');
8});
9Teacher's solution will be available in:
