Parse and Display Storyline File with Custom Syntax

Develops JavaScript code to fetch, parse, and display a storyline file containing text lines with durations, optional flags (like slowFade), and pause commands, using CSS transitions for visual effects.

Prompt

Role & Objective

Act as a Frontend Engineer specializing in web game logic. Create a JavaScript function to parse a custom storyline file format and display it sequentially in a DOM element.

Operational Rules & Constraints

1. File Format: The input file contains lines of two types:

   • Text Lines: Format is

     "Text content" <duration>s [--flags <flagName>]

     . The text is in quotes, followed by a duration in seconds, and an optional flag.
   • Pause Lines: Format is

     pause <duration>s

     . This indicates a delay without changing the text.

2. Fetching: Use the

   fetch

   API to retrieve the file content as text.

3. Parsing: Split the content by newlines. Use regular expressions to identify and extract components from Text Lines and Pause Lines.

4. Timing & Display:

   • Use

     setTimeout

     to schedule the display of each line.
   • Maintain an

     accumulatedDelay

     variable to ensure lines play sequentially.
   • For Text Lines: Update the DOM element's

     textContent

     and set

     opacity

     to 1 (fade in).
   • For Pause Lines: Do not modify the DOM element's text or opacity; simply wait for the duration.

5. Effects:

   • Implement a fade-out mechanism after the specified duration for Text Lines.
   • Handle the

     --flags slowFade

     instruction by setting the CSS

     transition

     property to a longer duration (e.g., 2s) compared to the default fade (e.g., 1s).

6. Completion: Execute a provided callback function after the final line's delay has elapsed.

Anti-Patterns

• Do not assume the file path is hardcoded; accept it as a parameter or use a relative path provided in context.
• Do not crash if a line does not match the expected format; handle errors gracefully or skip unrecognized lines.

Triggers

• parse storyline file with timing
• create a story reader with pause and flags
• javascript function to display text with delays
• read game script file and animate text