Uncaught TypeError: Cannot read properties of undefined (reading '500')

JavaScript
1

html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <link rel="stylesheet" href="./styles.css">
    
  </head>
  <body>
<input  id= "number"></input>
<button id= "convert-btn">Convert</button>
<div id= "output"></div>
<script src= "./script.js"></script>
  </body>
</html>

const inputNumber = document.getElementById("number");
const convert = document.getElementById("convert-btn");
const outputElement = document.getElementById("output");

const numeral = [
  ["M", 1000]
  ["CM", 900]
  ["D", 500]
  ["CD", 400]
  ["C", 100]
  ["XC", 90]
  ["L", 50]
  ["XL", 40]
  ["X", 10]
  ["IX", 9]
  ["V", 5]
  ["IV", 4]
  ["I", 1]
];

input.addEventListner("keydown", e => {
  if(e.key === "Enter"){
    convert.click()
  }
})

convert.addEventListener("click", () => {
const value = input.value;
if(!value) {
  output.innerText = "Please enter a valid number"
} else if(value < 0){
  output.innerText = "Please enter a number greater than or equal to 1"
} else if(value > 3999){
  output.innerText = "Please enter a number less than or equal to 3999"
  }
})
2

Can you post all of your code and a link to the challenge?
Note: The error message you’re encountering, “Uncaught TypeError: Cannot read properties of undefined (reading ‘500’)”, typically occurs when you try to access a property of an object that is undefined

3 
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <link rel="stylesheet" href="./styles.css">
    
  </head>
  <body>
<input  id= "number"></input>
<button id= "convert-btn">Convert</button>
<div id= "output"></div>
<script src= "./script.js"></script>
  </body>
</html>

this the rest of it this the roman numeral project the error starter once i coded convert.addListener and down

5

I’ve edited your code for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

Pre-formatted-text
Pre-formatted-text1356×380 401 KB

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (').

6

Your code has several issues

Array items should have a comma after each one

You misspelled listener

You never define input anywhere in your code. Look at the variables you declared

7

That is an interesting error message.

  1. It will use the last element of the accessor array.
[1,2,3][0,2] // 3
// same as
[1,2,3][2] // 3
  1. With that in mind, we can see that this is undefined (["M", 1000] at index 900)
["M", 1000]["CM", 900] // undefined
// same as
["M", 1000][900] // undefined
  1. The next step is to access undefined using ["D", 500] (so index 500 into undefined)
["M", 1000]["CM", 900]["D", 500] // Uncaught TypeError: Cannot read properties of undefined (reading '500')
// same as
undefined[500]

That is how I understand it anyway. Perfectly normal…nothing to see here.

8

thanks i been up since last night a little brain dead lol

9

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