This morning I was improving a bit my blog, and I found this piece of code, this is simply a validation that I am doing on a component that I create for Astro:

if (typeof text !== "string") {
  throw new Error("text must be a string")
}

if (typeof maxLength !== "number") {
  throw new Error("maxLength must be a number")
}

if (typeof addEllipsis !== "boolean") {
  throw new Error("addEllipsis must be a boolean")
}

throw new Error is not incorrect, but it is generic, the TypeError object is more specific and is commonly used for errors that occur when a value is not of the expected type.

So as a personal note I’m going to post all the built-in error objects that JavaScript has so I know when to use them.

• Error: This is the generic error object in JavaScript. It is used to represent any type of error that is not covered by the other error objects. This object includes a “message” property that specifies an error message.

  throw new Error("This is a generic error")
  

• SyntaxError: This is used when there is a syntax error in the JavaScript code. This object includes a “message” property that specifies an error message.

  throw new SyntaxError("This is a syntax error")
  

• TypeError: This is used when a type error occurs, such as attempting to call a function on an object that is not a function. This object includes a “message” property that specifies an error message.

  throw new TypeError("This is a type error")
  

• RangeError: This is used when a range error occurs, such as attempting to create an array with a negative number of elements. This object includes a “message” property that specifies an error message.

  throw new RangeError("This is a range error")
  

• ReferenceError: This is used when attempting to access a variable that is not defined. This object includes a “message” property that specifies an error message.

  throw new ReferenceError("This variable is not defined")
  

• URIError: This is used when an error occurs in a URI, such as attempting to decode an invalid URI. This object includes a “message” property that specifies an error message.

  throw new URIError("This is an invalid URI")
  

You can find more informacion in MDN Error.

And did you know that you could create even your own errors? :)

class TriangleError extends Error {
  constructor(message) {
    super(message)
    this.name = "TriangleError"
  }
}

Then:

function calculateTriangleArea(base, height) {
  if (isNaN(base) || isNaN(height) || base <= 0 || height <= 0) {
    throw new TriangleError("The arguments must be positive numbers.")
  }

  return (base * height) / 2
}

try {
  const area = calculateTriangleArea(5, "10")
} catch (error) {
  if (error instanceof TriangleError) {
    console.error(`Error: ${error.message}`)
  } else {
    console.error(error)
  }
}

Regards…