javascript - 如何将字符串解析为比较运算符？

Question

我实现了一种根据指定选项过滤商品的方法。该方法以包含搜索参数的选项对象作为参数，例如:{name: "item 2", Price: "<= 1000", count: "> 2"}，每个选项都是可选的。该方法必须返回带有商品的过滤数组。过滤产品依据(选项)。 我设法按名称进行过滤。告诉我如何正确地按数字过滤，以便过滤器调用如下所示:

console.log(shop.filterProductBy({
name: "product 1",
count: ">1",
price: "<=1000"}));

“count”和“price”需要与比较运算符一起解析，比较运算符设置过滤器的范围，这里有一个函数可以做到这一点，我如何在我的方法中实现这个函数，一切会起作用吗？

function parseCompOperator(oString, lhs) {
    if (oString.match("(?:<|>)=?\\d+") === null) {
        return "Invalid input";
    }

    let rator = oString.match("(?:<|>)=?")[0];
    let rhs = oString.match("\\d+")[0] * 1;

    if (rator === '>') {
        return (lhs > rhs);
    }
    else if (rator === '<') {
        return (lhs < rhs);
    }
    else if (rator === '>=') {
        return (lhs >= rhs);
    }
    else if (rator === '<=') {
        return (lhs <= rhs);
    }
}

所有代码:

//Product Creation Class
class Product {
    constructor(name, count, price) {
        this.name = name;
        this.count = count;
        this.price = price;
    }
}
//Сlass where products are recorded
class Shop {
    constructor(products) {
        this.products = [];
    }
    //method for adding a product
    addProduct(newProduct) {
        this.products.push(newProduct);
    }
    //method for filtering products by specified parameters
    filterProductBy(options) {
        const optionName = options.name,
            optionCount = options.count,
            optionPrice = options.price;

        const filters = {
            byName: function (actualName, optionName) {
                return (actualName === undefined) || (actualName === optionName);
            },

            byCount: function (actualCount, optionCount) {
                return (actualCount === undefined) || (actualCount === optionCount);
            },

            byPrice: function (actualPrice, optionPrice) {
                return (actualPrice === undefined) || (actualPrice === optionPrice);
            }
    };
        return this.products.filter(
            (product) => filters.byName(product.name, optionName)
            || filters.byCount(product.count, optionCount)
            || filters.byPrice(product.price, optionPrice));
        }
}
const shop = new Shop();
shop.addProduct(new Product("product 1", 1, 2000));
shop.addProduct(new Product("item 2", 2, 100));
shop.addProduct(new Product("some 3", 3, 500));
shop.addProduct(new Product("anything 4", 4, 1000));
console.log(shop.filterProductBy({
    name: "product 1",
    count: ">1",
    price: ">=500"

}));

Answer 1

您可以使用一个对象，其中运算符作为键，函数作为值，例如

var operators = {
        '===': function (a, b) { return a === b; },
        '==': function (a, b) { return a == b; },
        '<=': function (a, b) { return a <= b; },
        '>=': function (a, b) { return a >= b; },
        '<': function (a, b) { return a < b; },
        '>': function (a, b) { return a > b; }
    };

使用时，采用分隔的运算符和要比较的两个值。

您可以省略对运算符的检查并采用函数作为值，例如

return operators[operator](leftValue, rightValue);