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JavaScript Katas: Repeat it

July, 2020

Intro 🌐

Problem solving is an important skill, for your career and your life in general.

That’s why I take interesting katas of all levels, customize them and explain how to solve them.


Understanding the Exercise❗

First, we need to understand the exercise! If you don’t understand it, you can’t solve it!.

My personal method:

  1. Input: What do I put in?
  2. Output: What do I want to get out?

Today’s exercise

Source: Codewars

Write a function repeatIt, that accepts two parameters: inputString and repetitions.

Given a string, e.g. "Hi", and a number of repetitions, e.g. 2, return a string that repeats the input string n number of times, e.g. "HiHi":

If the input is not a string, return “Not a string”.


Input: a string and a number.

Output: a string.


Thinking about the Solution 💭

I think I understand the exercise (= what I put into the function and what I want to get out of it).

Now, I need the specific steps to get from input to output.

I try to do this in small baby steps.

  1. Check if it is a string
  2. If yes, then repeat it x times

Example:

  • Input: "Hi", 2
  • Check if it is a string: true
  • Iteration 1: add it to results => "Hi"
  • Iteration 2: add it to results => "HiHi"
  • Output: "HiHi"

Implementation (native method) ⛑

function repeatIt(inputString, repetitions) {
  // check if it is a string
  if (typeof inputString !== "string") {
    return "Not a string";
  }

  // repeat it x times
  return inputString.repeat(repetitions);
}

Result

console.log(repeatIt("Hi", 2));
// "HiHi" ✅

console.log(repeatIt(999, 1));
// "Not a string" ✅

Implementation (for loop) ⛑

function repeatIt(inputString, repetitions) {
  // check if it is a string
  if (typeof inputString !== "string") {
    return "Not a string";
  }

  // variable for result
  let result = "";

  // repeat it x times
  for (let i = 0; i < repetitions; i++) {
    // add it to result
    result += inputString;
  }

  return result;
}

Result

console.log(repeatIt("Hi", 2));
// "HiHi" ✅

console.log(repeatIt(999, 1));
// "Not a string" ✅

Playground ⚽

You can play around with the code here


Next Part ➡️

Great work!

We learned how to use typeof, repeat and for.

I hope that you can use your new learnings to solve problems more easily!

Next time, we’ll solve another interesting kata. Stay tuned!


If I should solve a specific kata, shoot me a message here.

If you want to read my latest stuff, get in touch with me!


Further Reading 📖


Questions ❔

  • How often do you do katas?
  • Which implementation do you like more? Why?
  • Any alternative solution?

miku86

Hi! I'm Michael 👋 I'm a Mentor & Educator & Senior Web Developer - I help you to reach your (career) goals.