使用 JavaScript 方法对项目进行排序

问：

我正在尝试使用排序方法，但它一直告诉我未定义 filteredProducts

用于对项目进行排序的代码

data() {
    return {
      MovieCategory: ["Action", "Adventure", "Family", "Comedy", "All"],
      filteredProducts: [],
    };

  methods: {
    filterMovies(category) {
      if (category == "All") {
        this.filteredProducts = this.products;
      } else {
        this.filteredProducts = this.products.filter(
          (product) => product.MovieCategory === category
        );
      }
    },

  sortItems() {
      this.filteredProducts = this.filteredProducts.sort((a, b) => {
        if (a.MovieCategory < b.MovieCategory) {
          return -1;
        } else {
          return 1;
        }
      });
    },