Method parse

www/js/_hyperscript.esm.js:9791–9816

* Parse when feature * @param {Parser} parser * @returns {WhenFeature | undefined}

(parser)

   * @returns {WhenFeature | undefined}
   */
  static parse(parser) {
    if (!parser.matchToken("when")) return;
    var exprs = [];
    do {
      parser.pushFollow("or");
      try {
        exprs.push(parser.requireElement("expression"));
      } finally {
        parser.popFollow();
      }
    } while (parser.matchToken("or"));
    for (var i = 0; i < exprs.length; i++) {
      var expr = exprs[i];
      if (expr.type === "symbol" && expr.scope === "local" && !expr.name.startsWith("$") && !expr.name.startsWith(":")) {
        parser.raiseError(
          "Cannot watch local variable '" + expr.name + "'. Local variables are not reactive. Use '$" + expr.name + "' (global) or ':" + expr.name + "' (element-scoped) instead."
        );
      }
    }
    parser.requireToken("changes");
    var start = parser.requireElement("commandList");
    parser.ensureTerminated(start);
    var feature = new _WhenFeature(exprs, start);
    parser.setParent(start, feature);
    return feature;
  }
  constructor(exprs, start) {
    super();
    this.exprs = exprs;