Have you ever gotten the warning message “cannot redeclare block-scoped variable” in TypeScript? If yes, let’s follow our article. We will help you learn about the cause of this error and how to fix it. Let’s start now!

When do you get the error “cannot redeclare block-scoped variable” in TypeScript?

When you get to start with TypeScript, you easily get the following example:

Cannot redeclare block-scoped variable

A TypeScript attribute is the cause of this problem. Any TypeScript code you create in a new file must follow one of the requirements listed below.

• You need to declare the file with its scope as a module.
• The declared file needs to be shared in a global scope.

The file followed the 2nd requirement. Because the global object has a name property, the variable name is already in the global scope in that situation. Additionally, let does not permit redeclaration. Combining these two factors, the error “cannot redeclare block-scoped variable” happened.

Let’s follow the next part to find the best way to fix this error.

Some solutions to solve the error “cannot redeclare block-scoped variable” in TypeScript

Solution 1: Adding the export {}

TypeScript must be informed that your file is a module with a separate scope. Any file containing import or export statements is considered a module by TypeScript. Add the line below as the first line of your TypeScript file to inform TypeScript that your file is a module.

export {};

The issue will be fixed by adding that single line. Therefore, your finished TypeScript file appears as seen below.

export {};
let name = "hi";

Solution 2: Using the namespace

Everything in a namespace is not included in the global scope, so classes or functions can be added there. Take a look at the example below:

namespace Greetings {
    function returnGreeting (greeting: string) {
        console.log(`The message from namespace Greetings is ${greeting}.`);
    }
}

If you use this method, your error will completely disappear, and your program will run well without any problems.

Solution 3: Transferring the declaration of that variable

If it suits your needs, you can also transfer the declaration of that variable to the onReady event handler or a function to solve this problem.

Conclusion

The solutions we give you above are the best ways to solve the error “cannot redeclare block-scoped variable” in TypeScript. We believe that you can quickly resolve your problem by using them. If you have any questions or issues with this error, please leave your comment below. We are always here to help you. Thank you for your reading!

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