One of the most foundational things to understand about JavaScript is that programs are made up of statements, and statements have slots for expressions. In this blog post, we'll dig into how these two structures work, and see how building an intuition about this can help us solve practical problems.

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This tutorial explains the difference between a “statement” and an “expression” in JavaScript. Most of those JSX rules you've had to memorize, and always forget to follow, are the result of this duality. This tutorial assumes that you're comfortable with basic JavaScript syntax, but is otherwise written to be beginner-friendly.

Statements Vs. Expressions

Link to this heading Expressions as statements

Link to this heading Practical implications in React

But…
A statement is more or less an expression too. In JavaScript, as well as Java, assigning a new value to a variable is an expression evaluated to the value of the variable:
<pre><code class="language-javascript">let value;

value = 5; /* Evaluates to 5 */
</code></pre>

Thank you! It was clear and easy to follow.