<code>useEffect</code> allows us to produce some side effects for our component. Anything that reaches outside of the component to do something. Like a network request or setting up timeouts and intervals. Their main job doesn't have to do with managing set or changing anything about the display of the component. 
<ul>
<li>By default useEffect runs after every re-render</li>
</ul>
We only run the code inside of the useEffect hook when the whenever the options inside of the array actually change, therefore, we can create a hook that only ever runs on mount by passing in an empty array. 
If we need useEffect to only run during the initial render and not for re-renders, we can leave an empty arrray on the dependency list:
<pre><code class="lang-`"> useEffect(() =&gt; {
 console.log("call useEffect");
 if (value &gt;= 1) {
 document.title = `New Messages (${value})`;
 }
 }, []);
</code></pre>

`useEffect` allows us to produce some side effects for our component. Anything that reaches outside of the component to do something. Like a network request or setting up timeouts and intervals. Their main job doesn't have to do with managing set or changing anything about the display of the component. 

- By default useEffect runs after every re-render

We only run the code inside of the useEffect hook when the whenever the options inside of the array actually change, therefore, we can create a hook that only ever runs on mount by passing in an empty array. 

If we need useEffect to only run during the initial render and not for re-renders, we can leave an empty arrray on the dependency list:

````
  useEffect(() => {
    console.log("call useEffect");
    if (value >= 1) {
      document.title = `New Messages (${value})`;
    }
  }, []);

```



Learner's notes on useEffect in React