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JavaScript: Properties

The data we use in our programs can have important properties, such as strings having length. As you will see later, this property is required to implement string conversion algorithms (e.g., string reversal). So how do you find out the length of a string? In many languages, string length is calculated with a special function, and it looks a bit like this:

import { length } from 'hexlet-basics/string';

const name = 'Robb';
console.log(length(name)); // => 4

In JavaScript, properties are built into the language. They are written with a dot right after a variable (or a constant):

const name = 'Robb';
const len = name.length;
console.log(len); // => 4

Properties are linked with the data they are taken from. For primitive types, e.g. strings, all property descriptions are described in the documentation. However, numbers have no properties at all.

JavaScript allows you to call properties that do not exist (e.g. in the case of typos). In this case their value is undefined:

const name = 'Robb';
console.log(name.whatIsThat); // => undefined

Self-сheck. What will console.log(name[name.length]) print for the variable name above? Why is the result like that?


Print the length of a string text.

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 🙄

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  • Read the String.length documentation. Note that the length of a string is equal to the number of characters in it. The length of an empty string, '', is 0.

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