tolocaledatestring('fr-fr', month) how to get month, first character must be in uppercase in javascript

You can achieve this by using the options parameter of toLocaleDateString() method to format the month as per your requirement. Here is an example:

index.tsx
const month = 7; // August (0-based index)

const options = {
  month: 'long',
  year: 'numeric',
  day: 'numeric',
  timeZone: 'UTC',
};

const locale = 'fr-fr';

const date = new Date(Date.UTC(2021, month));

const formattedDate = date.toLocaleDateString(locale, options);

const formattedMonth = formattedDate.charAt(0).toUpperCase() + formattedDate.slice(1, 3);

console.log(formattedMonth); // Aug
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In this example, we are setting options to format the date as "long" month name and "numeric" year and date, using "UTC" time zone. Then we are creating a Date object with the specified month value, and using toLocaleDateString() method to format it using the specified locale and options.

Finally, we are getting the formatted month string, capitalizing the first character, and returning the result.