Introduction to Query String

The query-string JavaScript library is a powerful tool designed to parse and stringify URL query strings. This allows developers to efficiently manage URL parameters, enhancing the functionality of web applications.

1. Parsing Query Strings

Convert a query string into a JavaScript object using the parse method.

  
    const queryString = require('query-string');
    const parsed = queryString.parse('?foo=bar&abc=xyz&abc=123');
    console.log(parsed);
    // Output: { foo: 'bar', abc: ['xyz', '123'] }
  

2. Stringifying Objects

Convert a JavaScript object into a query string with the stringify method.

  
    const queryString = require('query-string');
    const stringified = queryString.stringify({ foo: 'bar', abc: ['xyz', '123'] });
    console.log(stringified);
    // Output: 'foo=bar&abc=xyz&abc=123'
  

3. Parsing Arrays

Handle arrays in query strings seamlessly.

  
    const queryString = require('query-string');
    const parsed = queryString.parse('?ids=1,2,3');
    console.log(parsed);
    // Output: { ids: ['1', '2', '3'] }
  

4. Nested Objects

Parse and stringify nested objects effectively.

  
    const queryString = require('query-string');
    const parsed = queryString.parse('?user[name]=John&user[age]=30');
    console.log(parsed);
    // Output: { user: { name: 'John', age: '30' } }

    const stringified = queryString.stringify({ user: { name: 'John', age: 30 } });
    console.log(stringified);
    // Output: 'user%5Bname%5D=John&user%5Bage%5D=30'
  

5. Sorting Keys

Sort keys in a query string by enabling the sort option.

  
    const queryString = require('query-string');
    const stringified = queryString.stringify({ b: 'world', a: 'hello' }, { sort: true });
    console.log(stringified);
    // Output: 'a=hello&b=world'
  

6. Parsing Booleans

Convert query string values to booleans automatically.

  
    const queryString = require('query-string');
    const parsed = queryString.parse('?active=true&admin=false');
    console.log(parsed);
    // Output: { active: 'true', admin: 'false' }
  

Example Application

Below is an example of a simple Express.js application that uses query-string to manage URL parameters.

  
    const express = require('express');
    const queryString = require('query-string');

    const app = express();

    app.get('/search', (req, res) => {
      const parsedQuery = queryString.parse(req.url.split('?')[1]);
      res.send(`Parsed Query: ${JSON.stringify(parsedQuery)}`);
    });

    app.listen(3000, () => {
      console.log('Server is running on port 3000');
    });
  

With query-string, managing URL parameters becomes a breeze, improving your web application’s functionality and SEO.

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