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curriculum/challenges/english/blocks/learn-recursion-by-building-a-decimal-to-binary-converter/646477c82475ffaf0c3c0771.md

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--description--

While asynchronous, or async, code can be difficult to understand at first, it has many advantages. One of the most important is that it allows you to write non-blocking code.

For example, imagine you're baking a cake, and you put the cake in the oven and set a timer. You don't have to sit in front of the oven waiting the entire time – you can wash dishes, read a book, or do anything else while you wait for the timer to go off.

Async code works in a similar way. You can start an async operation and other parts of your code will still work while that operation is running.

You'll learn more about async code in future projects, but the setTimeout() function is a good introduction.

Add a 1500 millisecond delay before the text "Camp" is logged to the console.

--hints--

You should add a third setTimeout() function to your showAnimation() function.

js
assert.lengthOf(
  code.match(/setTimeout\(/g),
  3
);

You should pass a callback function as the first argument to the new setTimeout() function.

js
assert.lengthOf(
  code.match(/setTimeout\(\s*\(\s*\)\s*=>\s*\{?|setTimeout\(\s*function\s*\(\s*\)\s*\{/g),
  3
);

Within the new setTimeout() function's callback, you should log the text Camp to the console.

js
assert.match(code, /setTimeout\(\s*\(\s*\)\s*=>\s*\{?\s*console\.log\(\s*('|"|`)\s*Camp\s*\1\s*\)|setTimeout\(\s*function\s*\(\s*\)\s*\{\s*console\.log\(\s*('|"|`)\s*Camp\s*\2\s*\)/i);

You should pass 1500 as the second argument to the new setTimeout() function.

js
assert.match(code, /console\.log\(\s*('|"|`)\s*Camp\s*\1\s*\)\s*;?\s*\}?\s*,\s*1500\s*\)/);

--seed--

--seed-contents--

html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Decimal to Binary Converter</title>
    <link rel="stylesheet" href="styles.css" />
  </head>
  <body>
    <h1>
      Decimal to Binary 

      Converter
    </h1>
    <section class="input-container">
      <label for="number-input">Enter a decimal number:</label>
      <input
        value=""
        type="number"
        name="decimal number input"
        id="number-input"
        class="number-input"
      />
      <button class="convert-btn" id="convert-btn">Convert</button>
    </section>
    <section class="output-container">
      <output id="result" for="number-input"></output>
      <h2>Call stack</h2>
      <div id="animation-container"></div>
    </section>
    <script src="script.js"></script>
  </body>
</html>
css
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --light-grey: #f5f6f7;
  --dark-blue: #1b1b32;
  --orange: #f1be32;
}

body {
  display: flex;
  flex-direction: column;
  align-items: center;
  font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console,
    monospace;
  font-size: 1.125rem;
  color: var(--light-grey);
  background-color: var(--dark-blue);
  padding: 0 4px;
}

h1 {
  font-size: 2.125rem;
  text-align: center;
  margin: 20px 0;
}

h2 {
  font-size: 1.5rem;
  text-align: center;
  margin: 20px 0;
}

.input-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
  justify-content: center;
  align-items: center;
  width: clamp(320px, 50vw, 460px);
  margin: 10px auto;
}

.input-container label {
  white-space: nowrap;
  word-spacing: -6px;
}

.convert-btn {
  font-size: inherit;
  font-family: inherit;
  background-color: var(--orange);
  width: 100%;
  height: 2rem;
  padding: 0 6px;
  border: none;
  border-radius: 2px;
  cursor: pointer;
}

.number-input {
  font-size: inherit;
  padding: 0.3rem;
  width: 100%;
}

.output-container {
  margin-inline: auto;
  width: clamp(320px, 50vw, 460px);
}

#result {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  text-align: center;
  min-height: 80px;
  margin-block-start: 20px;
  padding: 15px;
  border: 2px solid var(--orange);
  border-radius: 2px;
}

#animation-container {
  display: flex;
  flex-direction: column-reverse;
  justify-content: end;
  gap: 1rem;
  margin-block-end: 1rem;
  min-height: 40vh;
  border: 2px dashed var(--orange);
  padding: 1rem;
}

.animation-frame {
  font-family: -apple-system, BlinkMacSystemFont, avenir next, avenir, segoe ui,
    helvetica neue, helvetica, Cantarell, Ubuntu, roboto, noto, arial,
    sans-serif;
  padding: 15px 10px;
  border: 5px solid var(--orange);
  font-size: 1.2rem;
  text-align: center;
}

@media screen and (min-width: 36em) {
  body {
    font-size: 1rem;
  }

  .input-container {
    flex-direction: row;
    width: unset;
  }

  .number-input {
    width: unset;
  }
}
js
const numberInput = document.getElementById("number-input");
const convertBtn = document.getElementById("convert-btn");
const result = document.getElementById("result");

const decimalToBinary = (input) => {
  if (input === 0 || input === 1) {
    return String(input);
  } else {
    return decimalToBinary(Math.floor(input / 2)) + (input % 2);
  }
};

const showAnimation = () => {
  setTimeout(() => {
    console.log("free");
  }, 500);
  setTimeout(() => {
    console.log("Code");
  }, 1000);
--fcc-editable-region--
  console.log("Camp");
--fcc-editable-region--
};

const checkUserInput = () => {
  const inputInt = parseInt(numberInput.value);

  if (!numberInput.value || isNaN(inputInt) || inputInt < 0) {
    alert("Please provide a decimal number greater than or equal to 0");
    return;
  }

  if (inputInt === 5) {
    showAnimation();
    return;
  }

  result.textContent = decimalToBinary(inputInt);
  numberInput.value = "";
};

convertBtn.addEventListener("click", checkUserInput);

numberInput.addEventListener("keydown", (e) => {
  if (e.key === "Enter") {
    checkUserInput();
  }
});