curriculum/challenges/english/blocks/learn-recursion-by-building-a-decimal-to-binary-converter/64007367d54d2a7efbf44fcf.md
Next, you need to check if the value returned by the parseInt() function is a number or not.
To do that, you can use the isNaN() function. This function takes in a string or number as an argument, and returns true if it evaluates to NaN. For example:
isNaN("test"); // true
isNaN(2); // false
isNaN("3.5"); // false
Update the second condition in your if statement to use the isNaN() function to check if the value returned by parseInt() is NaN.
Also, as we mentioned in step 1 that we are considering only positive numbers, we should add a third condition in if statement to check whether the number is less than 0 (i.e negative numbers).
6 < 0; // false
-1 < 0; // true
-8 < 0; // true
0 < 0; //false
You should wrap the value returned by parseInt() in the isNaN() function. And add a third condition which checks the value returned by parseInt() to be less than 0.
assert.match(String(checkUserInput), /if\s*\(\s*!\s*numberInput\s*\.\s*value\s*\|\|\s*isNaN\(\s*parseInt\(\s*numberInput\s*\.\s*value\s*\)\s*\)\s*\|\|\s*parseInt\(\s*numberInput\s*\.\s*value\s*\)\s*\<\s*0\s*\)\s*\{/);
The body of your if statement within checkUserInput should be empty.
assert.match(String(checkUserInput), /if\s*\(\s*.+\s*\)\s*\{\s*\}/);
<!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>
*,
*::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;
}
}
const numberInput = document.getElementById("number-input");
const convertBtn = document.getElementById("convert-btn");
const result = document.getElementById("result");
const checkUserInput = () => {
--fcc-editable-region--
if (!numberInput.value || parseInt(numberInput.value)) {
}
--fcc-editable-region--
console.log(numberInput.value);
};
convertBtn.addEventListener("click", checkUserInput);
numberInput.addEventListener("keydown", (e) => {
if (e.key === "Enter") {
checkUserInput();
}
});