regexper-static/src/js/parser/javascript/parser_state.js

// State tracking for an in-progress parse and render.
export default class ParserState {
  // - __progress__ - DOM node to update to indicate completion progress.
  constructor(progress) {
    // Tracks the number of capture groups in the expression.
    this.groupCounter = 1;
    // Cancels the in-progress render when set to true.
    this.cancelRender = false;
    // Warnings that have been generated while rendering.
    this.warnings = [];

    // Used to display the progress indicator
    this._renderCounter = 0;
    this._maxCounter = 0;
    this._progress = progress;
  }

  // Counts the number of in-progress rendering steps. As the counter goes up,
  // a maximum value is also tracked. The maximum value and current render
  // counter are used to calculate the completion process.
  get renderCounter() {
    return this._renderCounter;
  }

  set renderCounter(value) {
    if (value > this.renderCounter) {
      this._maxCounter = value;
    }

    this._renderCounter = value;

    if (this._maxCounter && !this.cancelRender) {
      this._progress.style.width = ((1 - this.renderCounter / this._maxCounter) * 100).toFixed(2) + '%';
    }
  }
}