Oops! Looks like the property you're trying to access doesn't exist in the type 'Registration'. Better double check your code!

I'm currently working on a project using JavaScript and Typescript. I've run into an issue with a function that checks for duplicates in an array, specifically with the error message shown below alongside a snippet of the code.

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);
   };

If anyone has any insights or suggestions on how to resolve this issue, it would be greatly appreciated. Thank you!

Answer №1

This indicates that the function toLocaleLowerCase() cannot be applied to your object of type Registration. The method toLocaleLowerCase() is specifically for strings, so unless you can convert your Registration object into a string, it will not work correctly. Additionally, if the property Registration.fullname is optional and possibly undefined, this could also be causing the error.

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