Task: Create a function that turns a string into a Mexican Wave. You will be passed a string and you must return that string in an array where an uppercase letter is a person standing up.
<pre><code class="lang-javascript">let mexicanWave = str.slice(0, i) + str[i].toUpperCase() + str.slice(i + 1);
</code></pre>
Above code aims to create a string where one character is capitalized (turned into uppercase), and the rest of the string is unchanged.
Let's break it down:
<ol>
<li><code>str.slice(0, i)</code>: This is creating a new string that includes the characters from the start of the original string (<code>str</code>) up to but not including the <code>i</code>th character. <code>slice</code> is a method provided by JavaScript's String prototype that returns a portion of the string. 
</li>
<li><code>str[i].toUpperCase()</code>: This is getting the <code>i</code>th character from the original string (<code>str[i]</code>) and capitalizing it using the <code>toUpperCase</code> method, also provided by the String prototype. 
</li>
<li><code>str.slice(i + 1)</code>: This is creating a new string that includes all characters from the original string (<code>str</code>) starting from the character after the <code>i</code>th character. 
</li>
<li>The <code>+</code> operators are then concatenating these three strings together to form a new string. The <code>i</code>th character of this new string is capitalized, and the rest of the string is the same as the original string.
</li>
</ol>

Task:  
Create a function that turns a string into a Mexican Wave. You will be passed a string and you must return that string in an array where an uppercase letter is a person standing up.

```javascript
let mexicanWave = str.slice(0, i) + str[i].toUpperCase() + str.slice(i + 1);
```

Above code aims to create a string where one character is capitalized (turned into uppercase), and the rest of the string is unchanged.

Let's break it down:

1. `str.slice(0, i)`: This is creating a new string that includes the characters from the start of the original string (`str`) up to but not including the `i`th character. `slice` is a method provided by JavaScript's String prototype that returns a portion of the string.  
    
2. `str[i].toUpperCase()`: This is getting the `i`th character from the original string (`str[i]`) and capitalizing it using the `toUpperCase` method, also provided by the String prototype.  
    
3. `str.slice(i + 1)`: This is creating a new string that includes all characters from the original string (`str`) starting from the character after the `i`th character.  
    
4. The `+` operators are then concatenating these three strings together to form a new string. The `i`th character of this new string is capitalized, and the rest of the string is the same as the original string.