Method nullCheck

www/js/_hyperscript.js:2652–2656

(value, elt)

      return typeof ctor === "function" && value instanceof ctor;
    }
    nullCheck(value, elt) {
      if (value == null) {
        throw new Error("'" + elt.sourceFor() + "' is null");
      }
    }
    isEmpty(value) {
      return value == void 0 || value.length === 0;
    }