Function firstMap

firstMap<T, R>(fn: (arg: T) => void | R, properties: T[]): void | R

Takes a function and an array of values, applies the function to each value in sequence, and returns the first non-undefined/null result. Useful for trying multiple possible inputs until finding one that produces a valid result.

Type Parameters

Parameters

fn: (arg: T) => void | R
The function to apply to each value
properties: T[]
Array of values to try the function on

Returns void | R

The first non-undefined/null result from applying the function, or undefined if all attempts fail

Example

// Parse number from different formats
const getNumber = (s: string) => s.match(/\d+/)?.[0];
firstMap(getNumber, ["no nums", "abc123", "def"]) // Returns "123"

// Find first valid item
const isValid = (x: number) => x > 10 ? x : undefined;
firstMap(isValid, [5, 8, 15, 20]) // Returns 15

// Complex transformations
const parseDate = (s: string) => {
  const date = new Date(s);
  return isNaN(date.getTime()) ? undefined : date;
};
firstMap(parseDate, ["invalid", "2023-01-01", "also invalid"])

Source

export function firstMap<T, R>(fn: (arg: T) => R | void, properties: T[]): R | void {
  //try {
  for (const prop of properties) {
    const result = fn(prop);
    if (result !== undefined && result !== null) {
      return result;
    }
  }
  return undefined;
  // } catch (error) {
  //   //console.error("ERROR in firstMap:", error);
  //   throw
  //   return undefined;
  // }
}