Method constructor

static/katex/katex.mjs:90–143

(message, // The error message
  token)

class ParseError {
  // Error position based on passed-in Token or ParseNode.
  constructor(message, // The error message
  token) // An object providing position information
  {
    this.position = void 0;
    let error = "KaTeX parse error: " + message;
    let start;
    const loc = token && token.loc;

    if (loc && loc.start <= loc.end) {
      // If we have the input and a position, make the error a bit fancier
      // Get the input
      const input = loc.lexer.input; // Prepend some information

      start = loc.start;
      const end = loc.end;

      if (start === input.length) {
        error += " at end of input: ";
      } else {
        error += " at position " + (start + 1) + ": ";
      } // Underline token in question using combining underscores


      const underlined = input.slice(start, end).replace(/[^]/g, "$&\u0332"); // Extract some context from the input and add it to the error

      let left;

      if (start > 15) {
        left = "…" + input.slice(start - 15, start);
      } else {
        left = input.slice(0, start);
      }

      let right;

      if (end + 15 < input.length) {
        right = input.slice(end, end + 15) + "…";
      } else {
        right = input.slice(end);
      }

      error += left + underlined + right;
    } // Some hackery to make ParseError a prototype of Error
    // See http://stackoverflow.com/a/8460753


    const self = new Error(error);
    self.name = "ParseError"; // $FlowFixMe

    self.__proto__ = ParseError.prototype; // $FlowFixMe

    self.position = start;
    return self;
  }

} // $FlowFixMe More hackery