Good evening! Here's our prompt for today.
Detecting JavaScript Data Types: A Universal Method
The Challenge
Imagine a universe of data types in JavaScript! It's a colorful world with characters like Array, ArrayBuffer, Map, Set, Date, and the mysterious Function. Your mission, should you choose to accept it, is to create a universal method that identifies these inhabitants by their data type name.
Constraints:
- The function should take only one argument—the data object.
- We want a universal approach; using multiple
ifconditions to list and detect each data type is a no-go.
Example Usage
For the function detectType(), the following should hold true:
1detectType(1); // Output: 'number'
2detectType(new Map()); // Output: 'map'
3detectType([]); // Output: 'array'
4detectType(null); // Output: 'null'
Try to solve this here or in Interactive Mode.
How do I practice this challenge?
xxxxxxxxxxfunction detectType(data) { return Object.prototype.toString .call(data) .slice(1, -1) .split(" ")[1] .toLowerCase();}Here's how we would solve this problem...
How do I use this guide?
The Visual Insight
Picture your data types as distinct islands in an archipelago. Your function is the explorer boat that sails between these islands and reads the name sign at each dock. It doesn't matter which island you land on; you'll always find the right name!
Crafting the Solution
Utilize JavaScript’s Native Typeof: Our first instinct might be to reach for JavaScript's built-in
typeofoperator. However,typeoflacks the specificity needed for custom and built-in objects likeArrayorDate. It often just returns 'object', which doesn't help us much.Object’s ToString Method: In JavaScript, the Object prototype has a
toStringmethod that, when called directly, provides more specific information thantypeof.
A Deep Dive Into the Universal DataType Detector
How to Solve This: A Step-by-Step Guide
Step 1: Summon the Power of Object.prototype.toString
First, we call upon Object.prototype.toString.call(data). This incantation returns a raw string that holds clues about the data type.
Step 2: String Alchemy
Our next mission is to mine the useful nuggets—our data type—from this raw string.
The Code That Makes It All Happen
Behold the code that brings these steps to life.
1function detectType(data) {
2 const rawType = Object.prototype.toString.call(data);
3 return rawType.slice(8, -1).toLowerCase();
4}The Under-the-Hood Mechanics
Our solution may look simple, yet it elegantly fulfills the requirement to be generic. We achieve this by invoking the Object.prototype.toString method, which acts like an oracle. The oracle speaks in riddles: it returns the data type enveloped in a string format like [object dataType].
Deciphering the Oracle's Message
The answer to our quest lies between the square brackets in the oracle's message. We slice this string to get that part. Then, to make it universally readable, we convert it to lowercase.
The Alternate Path
If you prefer another twist, you can modify the function to slice from the first character onward and then split the string using a space delimiter. This will still get you to the treasure—the data type.
1function detectType(data) {
2 return Object.prototype.toString
3 .call(data)
4 .slice(1, -1)
5 .split(" ")[1]
6 .toLowerCase();
7}The Grand Conclusion
Now, you're equipped with a detectType function that's like a Swiss Army knife for data types. Not only does it elegantly solve the problem, but it also does so in a way that's adaptable to future challenges.
One Pager Cheat Sheet
- Create a generic, parameter-accepting method that returns a string of the
data typeof the given input. - We can parse a given data's type by calling
Object.prototype.toString()and slicing/splitting the result.
This is our final solution.
To visualize the solution and step through the below code, click Visualize the Solution on the right-side menu or the VISUALIZE button in Interactive Mode.
xxxxxxxxxxfunction detectType(data) { return Object.prototype.toString .call(data) .slice(1, -1) .split(" ")[1] .toLowerCase();}Alright, well done! Try another walk-through.
If you had any problems with this tutorial, check out the main forum thread here.
