How to filter an array by string number with operators ?

Question

I implemented a method for filtering goods on the specified options. The method takes as an argument an options object that contains parameters for searching, for example: {name: "item 2", price: "<= 1000", count: "> 2"}, each of the options is optional. The method must return a filtered array with the goods. filterProductBy (options).

I managed to filter by name. Tell me how to properly filter by the number so that the filter call looks like this:

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

Code:

//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));

GalAbra · Accepted Answer · 2018-06-09 10:15:13Z

Your problem involves multiple sub-questions.
I think the most important one is How to parse a string into a comparison operator?

This is a primary implementation you can take further:

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);
  }
}


console.log(parseCompOperator(">1", 1));
console.log(parseCompOperator("<=1", 1));
console.log(parseCompOperator(">1", 3));

The regex I was using ((?:<|>)=?\\d+) matches the pattern of a comparison operator (>, <, <= or >=), followed by a number.
After making sure the input is valid, I separated the operator from the number and explicitly compared them.

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