What is the difference between 'throw new Error' and 'throw someObject' in javascript?

In JavaScript, both throw new Error and throw someObject can be used to throw exceptions, but they differ in structure and best practices.

Using throw new Error

When you use throw new Error(), JavaScript creates a proper Error object with standard properties:

try {
    throw new Error("Something went wrong");
} catch (error) {
    console.log("Name:", error.name);
    console.log("Message:", error.message);
    console.log("Stack:", error.stack ? "Available" : "Not available");
}

Name: Error
Message: Something went wrong
Stack: Available

Using throw someObject

You can throw any object, string, or primitive value. The thrown object is passed as-is to the catch block:

try {
    throw { 
        type: "CustomError", 
        message: "Custom error occurred",
        code: 404 
    };
} catch (error) {
    console.log("Type:", error.type);
    console.log("Message:", error.message);
    console.log("Code:", error.code);
    console.log("Stack:", error.stack ? "Available" : "Not available");
}

Type: CustomError
Message: Custom error occurred
Code: 404
Stack: Not available

Throwing Primitives

You can even throw strings or numbers directly:

try {
    throw "Simple error string";
} catch (error) {
    console.log("Caught:", error);
    console.log("Type:", typeof error);
}

console.log("---");

try {
    throw 404;
} catch (error) {
    console.log("Caught:", error);
    console.log("Type:", typeof error);
}

Caught: Simple error string
Type: string
---
Caught: 404
Type: number

Key Differences

Both Stop Execution

Regardless of what you throw, execution in the try block stops immediately:

try {
    console.log("Before throw");
    throw new Error("Error occurred");
    console.log("This will never execute");
} catch (error) {
    console.log("Caught:", error.message);
}

console.log("Execution continues after try-catch");

Before throw
Caught: Error occurred
Execution continues after try-catch

Conclusion

While both approaches throw exceptions and stop execution, throw new Error is recommended because it provides stack traces and follows JavaScript conventions. Use throw someObject only when you need custom error properties.