Filter an array of objects using a query string in Node.js

Question

I want to filter an array of objects based on a query string provided by the user in Node.js. There are packages such as rql or orql that can achieve this, but they seem to have problem with strings containing colon, such as time stamps. The code using rql:

var rql = require("rql/js-array");
var query1 = "time=lt=2018-08-06";
var query2 = "time=lt=2018-08-06T13:45:36.000Z"

var products = [
 {price:14.99, rating: 5, time: "2018-08-04T13:45:36.000Z"},
 {price:5.99, rating: 3, time: "2018-08-05T13:45:36.000Z"},
 {price: 16.5, rating:2, time: "2018-08-06T13:45:36.000Z"}];

console.log(rql.query(query1, {}, products)); // works
console.log(rql.query(query2, {}, products)); // gives error

The error message:

URIError: Unknown converter 2018-08-06T13
at stringToValue (/home/runner/node_modules/rql/parser.js:186:10)
at /home/runner/node_modules/rql/parser.js:99:20
at String.replace (<anonymous>)
at parse (/home/runner/node_modules/rql/parser.js:71:33)
at Object.query (/home/runner/node_modules/rql/js-array.js:358:10)

Similarly in orql:

var orql = require('orql');

var query1 = "time=lt=2018-08-06";
var query2 = "time=lt=2018-08-06T13:45:36.000Z"

var products = [
  {price:14.99, rating: 5, time: "2018-08-04T13:45:36.000Z"},
  {price:5.99, rating: 3, time: "2018-08-05T13:45:36.000Z"},
  {price: 16.5, rating:2, time: "2018-08-06T13:45:36.000Z"}];

console.log(orql(products, query1)); // works
console.log(orql(products, query2)); // gives error

The error message:

TypeError: Cannot read property 'name' of null
at rqlNodeToFunc (/home/runner/node_modules/orql/index.js:351:20)
at Function.rql.compile (/home/runner/node_modules/orql/index.js:65:14)
at rql (/home/runner/node_modules/orql/index.js:48:14)

Any idea how to do query on arrays of objects with timestamps?

fsinisi90 · Accepted Answer · 2018-08-19 13:46:53Z

1

Try using Lodash.

npm install lodash --save

Filter by date:

_.filter(products, function(element) { return element.time.includes('2018-08-04') })

Filter between dates:

let startDate = new Date('08/01/2018');
let endDate = new Date('08/06/2018');

_.filter(products, function (element) {
    let date = new Date(element.time);
    return date >= startDate && date <= endDate;
});

See it in action.

To get only one result use _.find instead of _.filter.

edited Aug 19, 2018 at 13:46

answered Aug 17, 2018 at 19:10

fsinisi90

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2 Comments

svakili Over a year ago

But can it do flexible queries, e.g. values between a and b? And can it be provided as a query by the user?

fsinisi90 Over a year ago

I've updated the answer with the code to find between dates. You could do what you want but providing your own logic. If you want to write SQL queries this is not the solution.

fsinisi90 · Accepted Answer · 2018-08-20 18:42:47Z

0

Seems like it's a bug in the rql parser, because the documentation says it supports "ISO UTC format without colon encoding":

Values in queries can be strings (using URL encoding), numbers, booleans, null, undefined, and dates (in ISO UTC format without colon encoding).

You can solve it adding the word string before the date.

var query2 = "time=lt=string:2018-08-06T13:45:36.000Z"

Or also encoding the colon (replacing it by %3A):

var query2 = "time=lt=2018-08-06T13%3A45%3A36.000Z";

edited Aug 20, 2018 at 18:42

answered Aug 19, 2018 at 13:42

fsinisi90

1,1681 gold badge17 silver badges51 bronze badges

1 Comment

svakili Over a year ago

It works! Amazing! Can you explain what was/is happening? I could not find anything in the documentation.

Bergur · Accepted Answer · 2018-08-17 21:22:54Z

Javascript also has filter method. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

var products = [
 {price:14.99, rating: 5, time: "2018-08-04T13:45:36.000Z"},
 {price:5.99, rating: 3, time: "2018-08-05T13:45:36.000Z"},
 {price: 16.5, rating:2, time: "2018-08-06T13:45:36.000Z"}
];

const byRating = function(rating) {
  return products.filter(product => product.rating === rating)
}

const withRatingFive = byRating (5); // 5 can be a parameter from your users.

const priceLowerThan = function(price) {
  return products.filter(product => product.price < price)
}

const cheapestProduct = priceLowerThan(6); // 6 can be a parameter from your users.

const dateBetween = function(start,end) {
  return products.filter(product => (product.time >= start && product.time <= end))
}

Just some examples that could help you in the right direction.

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