The ultimate guide to recursion interviews in JavaScript. Developed by FAANG engineers. Practice with real-world interview questions and get interview-ready in just a few hours.

If you’ve ever struggled with solving problems using recursion, or if you have to brush up your skills for an interview, this course is for you.

We'll start with the basics of what recursion is and why it’s important before diving into practicing solving actual questions. You’ll have access to detailed explanations and visualizations for each problem to help you along the way. 

By the time you have completed this course, you’ll be able to use all the concepts to solve complex real-world problems. We hope that through practicing recursion, you will be able to ace all recursion related questions in interviews at top tech companies.

Recursion for Coding Interviews in JavaScript

What is the output of the following code?
```javascript
function foo(x, p) {
    if (p == 0) {
      return 1;
    }
    else {
      return (x * foo(x, p - 1));
    }
}
    
// Driver Code
console.log(foo(2, 5));
```

What is the output of the following code?
<pre><code class="language-javascript">function foo(x, p) {
 if (p == 0) {
 return 1;
 }
 else {
 return (x * foo(x, p - 1));
 }
}
 
// Driver Code
console.log(foo(2, 5));
</code></pre>

What is the output of the following code?
```javascript
function foo(n) {
    if (n == 12) {
        return n;
    }
    else {
        return foo(n + 1);
    }
}

// Driver code
console.log(foo(3));
```

What is the output of the following code?
<pre><code class="language-javascript">function foo(n) {
 if (n == 12) {
 return n;
 }
 else {
 return foo(n + 1);
 }
}

// Driver code
console.log(foo(3));
</code></pre>

What is the output of the following code?
```javascript
function foo(n) {
    if (n == 0) {
        console.log("False");
        return;
    }
      
    else if (n == 1) {
        console.log("True");
        return;
    }
    
    else if (n % 2 == 0) {
        foo(n / 2);
    }
  
    else {
        console.log("False");
        return;
    }
}

// Driver Code
foo(64);
```

What is the output of the following code?
<pre><code class="language-javascript">function foo(n) {
 if (n == 0) {
 console.log(&quot;False&quot;);
 return;
 }
 
 else if (n == 1) {
 console.log(&quot;True&quot;);
 return;
 }
 
 else if (n % 2 == 0) {
 foo(n / 2);
 }
 
 else {
 console.log(&quot;False&quot;);
 return;
 }
}

// Driver Code
foo(64);
</code></pre>

What is the output of the following piece of code?
```javascript
function foo(i, j) {
    if (i == 0) {
        return j;
    }
    else {
        return foo(i - 1, i + j);
    }
}
      
// Driver Code
console.log(foo(4, 7));
```

What is the output of the following piece of code?
<pre><code class="language-javascript">function foo(i, j) {
 if (i == 0) {
 return j;
 }
 else {
 return foo(i - 1, i + j);
 }
}
 
// Driver Code
console.log(foo(4, 7));
</code></pre>

What is the output of the following piece of code?
```javascript
function foo(n) {
    if (n > 100) {
      return n - 5;
    }
    return foo(foo(n + 11));
}
  
// Driver Code
console.log(foo(45));
```

What is the output of the following piece of code?
<pre><code class="language-javascript">function foo(n) {
 if (n &gt; 100) {
 return n - 5;
 }
 return foo(foo(n + 11));
}
 
// Driver Code
console.log(foo(45));
</code></pre>

What should be the value of `testVariable` to satisfy the base case?
```javascript
function printPascal(testVariable) {
 if (testVariable == 0) {
 return [1];
 }

 else {
 var line = [1];
 previousLine = printPascal(testVariable - 1);

 for (let i = 0; i < previousLine.length - 1; i++) {
 line.push(previousLine[i] + previousLine[i + 1]);
 }
 line.push(1);
 } 
 return line;
}
```

What should be the value of <code>testVariable</code> to satisfy the base case?
<pre><code class="language-javascript">function printPascal(testVariable) {
 if (testVariable == 0) {
 return [1];
 }

 else {
 var line = [1];
 previousLine = printPascal(testVariable - 1);

 for (let i = 0; i &lt; previousLine.length - 1; i++) {
 line.push(previousLine[i] + previousLine[i + 1]);
 }
 line.push(1);
 } 
 return line;
}
</code></pre>

The value of a number raised to a certain power can be calculated recursively.

The value of a number raised to a certain power can be calculated recursively.

This Quiz will take maximum 10 minutes.

This Quiz will take maximum 10 minutes.

---
In the next chapter, we'll look at some string-related problems that use recursion.

Recursion Fundamentals

Iteration Vs Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Conclusion

Test Your Knowledge 3