{{alias}}( str, [options,] clbk[, thisArg] )
    Invokes a function for each character in a string.

    When invoked, the provided function is provided three arguments:

    - value: character.
    - index: starting character index.
    - str: input string.

    Parameters
    ----------
    str: string
        Input string over which to iterate.

    options: Object (optional)
        Options.

    options.mode: string (optional)
        Type of characters over which to iterate. The following modes are
        supported:

        - grapheme: grapheme clusters. Appropriate for strings containing visual
          characters which can span multiple Unicode code points (e.g., emoji).
        - code_point: Unicode code points. Appropriate for strings containing
          visual characters which are comprised of more than one Unicode code
          unit (e.g., ideographic symbols and punctuation and mathematical
          alphanumerics).
        - code_unit': UTF-16 code units. Appropriate for strings containing
          visual characters drawn from the basic multilingual plane (BMP) (e.g.,
          common characters, such as those from the Latin, Greek, and Cyrillic
          alphabets).

        Default: 'grapheme'.

    clbk: Function
        The function to invoke for each character in the input string.

    thisArg: any (optional)
        Execution context.

    Returns
    -------
    out: string
        Input string.

    Examples
    --------
    > var n = 0;
    > function fcn() { n += 1; };
    > {{alias}}( 'hello world!', fcn );
    > n
    12

    See Also
    --------