Compare the first character(s) of the provided context against one or more symbols

startsWithCharacters.js

//? an easy to follow, abstracted approach

/**
 * Compares first character of string against a character
 * @param {string} reference 
 * @returns {(character: string) => boolean}
 */
function startsWithCharacter(reference) {
  return character => reference.startsWith(
    character
  );
}

/**
 * Compares characters against a strings first character
 * @param {string} reference 
 * @returns {(characters: string[]) => boolean}
 */
function startsWithCharacters(reference) {
  return characters => characters.some(
    startsWithCharacter(reference)
  )
}

/**
 * Compares one or more characters against the first character in a string
 * @param {string} reference 
 * @returns {(variedInput: string|string[]) => boolean}
 */
function startsWithSymbol(reference) {
  return variedInput => startsWithCharacters(reference)(
    useOrWrapInArray(variedInput)
  )
}

//? ...an alternative "all in one" solution: shorter but less understandable

/**
 * Compares one or more characters against the first character in a string
 * @param {string} reference 
 * @returns {(variedInput: string|string[]) => boolean}
 */
function startsWithSymbols(reference) {
  return variedInput => (useOrWrapInArray(variedInput))
    .includes(Array.from(reference)[0])
}

//? utility methods for reuse

/**
 * Use array or wrap value in an array.
 * @param {*|*[]} - input value(s)
 * @returns {*[]}
 */
function useOrWrapInArray(variedInput) {
  return !Array.isArray(variedInput)
      ? [variedInput]
      : variedInput;
}