What Are Some Examples of Common JavaScript Errors?

As you've been programming in JavaScript, you've inevitably run into error messages. Understanding common error messages will help you debug more effectively and develop into a stronger programmer. The four common types of error messages are `SyntaxError`, `ReferenceError`, `TypeError`, and `RangeError`. A `SyntaxError` happens when you write something incorrectly in your code, like missing a parenthesis, or a bracket. Think of it like a grammar mistake in a sentence. Here is a common mistake developers make when creating arrays: ```js const arr = ["Beau", "Quincy" "Tom"] ``` Each array element needs to be separated by a comma, otherwise it will result in an error message. The second common JavaScript error is a `ReferenceError`. There are several types of `ReferenceError`s, triggered in different ways. The first type of `ReferenceError` would be not defined variables. ```js console.log(price); ``` In this example, we are trying to log the `price` variable to the console but it hasn't been defined. This will result in a `ReferenceError`. Another example of a `ReferenceError` is trying to access a variable, declared with `let` or `const`, before it has been defined: ```js console.log(b); const b = 50; ``` The example above will result in a `Cannot access 'b' before initialization` error. The third common error would be a `TypeError`. These errors occur when you try to perform an operation on the wrong type. Here is an example of trying to use the `map` method on an object: ```js const developerObj = { name: "Jessica", country: "USA", isEmployed: true }; developerObj.map() ``` This example will result in a `developerObj.map is not a function` error because the `map` method is used for arrays and not objects. The last common error we will look at is the `RangeError`. A `RangeError` happens when your code tries to use a value that's outside the range of what JavaScript can handle. Here is an example of assigning an invalid value to an array's length: ```js const arr = []; arr.length = -1; ``` Since an array's `length` has to be a non-negative integer, setting it to `-1` triggers a `RangeError`. As you continue to program in JavaScript, just be aware of these different types of errors you will probably encounter and why they are happening.