I am developing using JavaScript and Typescript. I have the following function to check if an array has duplicates, but I'm getting an error and not sure how to fix it. Below are the errors and code excerpts.

Error: Property 'toLocaleLowerCase' does not exist on type 'Registration'. ts(2339)

Registration.ts

export interface Registration { address: string; comment?: string; fullname?: string; }

JS file

const nameAlreadyExist = (name: any): void => { const nameExist = filteredRegistrationName.value.findIndex((registrationName) => registrationName.fullname.toLocaleLowerCase() === name.toLocaleLowerCase()); nameExist != -1 ? (existNameError.value = true) : (existNameError.value = false); };

Any insights would be greatly appreciated. Thanks!