Convert the name of an Excel column to number

JavaScript version
const getIndex = (col) => col.split('').reduce((prev, next) => prev * 26 + parseInt(next, 36) - 9, 0);
TypeScript version
const getIndex = (col: string): number => col.split('').reduce((prev, next) => prev * 26 + parseInt(next, 36) - 9, 0);
Examples
getIndex('A'); // 1
getIndex('B'); // 2
getIndex('C'); // 3
getIndex('Z'); // 26
getIndex('AA'); // 27
getIndex('AB'); // 28
getIndex('AC'); // 29
getIndex('AZ'); // 52
getIndex('AAA'); // 703
getIndex('AAB'); // 704