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Return correct value from recursive indexOf in JavaScript?
A computer pattern or idea called recursion is present in many programming languages, including JavaScript. It is a feature used to build a function that repeatedly calls itself, but with a smaller input each time, until the intended outcome of the code is realized.
In this article, we will return the correct value from a recursive indexOf() function in JavaScript. Let's dive into the article for a better understanding.
Understanding Recursive indexOf Implementation
The position of the first occurrence of a value in a string or array is returned by the indexOf() method. -1 is returned by the indexOf() method if the value cannot be found. The indexOf() is case sensitive.
Syntax
Following is the syntax for indexOf() ?
indexOf(searchElement) indexOf(searchElement, fromIndex)
Method 1: Recursive Search with Array Slicing
In the following example, we implement a recursive indexOf function using array slicing. We search for the index of element "c".
<!DOCTYPE html>
<html>
<body>
<script>
function search(array, value) {
if (array[0] === value) {
return 0;
}
if (array.length === 0) {
return -1;
}
const result = search(array.slice(1), value);
return result === -1 ? -1 : result + 1;
}
document.write("The indexOf c was: " +
search(["a", "b", "c", "d"], "c"));
</script>
</body>
</html>
The indexOf c was: 2
Method 2: Recursive Search with Index Parameter
This approach uses an index parameter to track the current position, making it more efficient than array slicing.
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<script>
function search(arr, value, i = 0) {
if (i >= arr.length) return -1;
if (arr[i] === value) return i;
return search(arr, value, i + 1);
}
let array = ["Raj", "Kamal", "Vikram", "Ravi"];
document.getElementById("tutorial").innerHTML = "The indexOf Vespa was: " + (search(array, "Vespa"));
</script>
</body>
</html>
The indexOf Vespa was: -1
The output shows "-1" because the value "Vespa" was not found in the array.
Method 3: Built-in indexOf Method
For comparison, here's how the built-in indexOf method works:
<!DOCTYPE html>
<html>
<body>
<p id="tutorial"></p>
<script>
const array = ['Bheem', 'Nayak', 'Ravi', 'Dora'];
const result = array.indexOf('Ravi');
document.getElementById("tutorial").innerHTML = "The indexOf() of required value was: " + result;
</script>
</body>
</html>
The indexOf() of required value was: 2
Comparison
| Method | Efficiency | Memory Usage | Use Case |
|---|---|---|---|
| Array Slicing | Lower | Higher | Educational purposes |
| Index Parameter | Better | Lower | Recursive implementation |
| Built-in indexOf | Best | Optimal | Production code |
Key Points
- Recursive indexOf functions demonstrate recursion concepts but are less efficient than built-in methods
- The index parameter approach is more memory-efficient than array slicing
- Both recursive methods return -1 when the element is not found, matching built-in behavior
Conclusion
Recursive indexOf implementations help understand recursion principles. While educational, use built-in indexOf() for production code as it's optimized and more efficient.
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