Node.js URLsearchParams API

Node.js is an open-source project widely used for the development of dynamic web applications. The URLSearchParams API in Node.js allows read and write operations on the URL query.

The URLSearchParams class is a global object and used with one of the four following constructors.

Constructors:

1. new URLSearchParams(): No argument constructor instantiates a new empty URLSearchParams object.
2. new URLSearchParams(string): Accepts a string as an argument to instantiate a new URLSearchParams object.

   var params = new URLSearchParams('user=abc&q=xyz');
   console.log(params.get('user'));
   console.log(params.get('q'));

   Output:

   abc
   xyz

3. new URLSearchParams(obj): Accepts an object with a collection of key-value pairs to instantiate a new URLSearchParams object. The key-value pair of obj are always coerced to strings. Duplicate keys are not allowed.

   const params = new URLSearchParams({
     user: 'ana',
     course: ['math', 'chem', 'phys']
   });
   console.log(params.toString());

   Output:

   user=ana&course=math%2Cchem%2Cphys

4. new URLSearchParams(iterable): Accepts an iterable object having a collection of key-value pairs to instantiate a new URLSearchParams object. Iterable can be any iterable object. Since URLSearchParams is iterable, an iterable object can be another URLSearchParams, where the constructor will create a clone of the provided URLSearchParams. Duplicate keys are allowed.

   // Using a Map object as it is iterable
   const map = new Map();
   map.set('West Bengal', 'Kolkata');
   map.set('Karnataka', 'Bengaluru');
   params = new URLSearchParams(map);
   console.log(params.toString());

   Output:

   West+Bengal=Kolkata&Karnataka=Bengaluru

Accessing the URL query:

• urlSearchParams.get(name): Returns the value of the first name-value pair that matches with the argument passed. If no such pair exists, null is returned.

  const myURL = new URL(
    'https://example.org/?abc=123&abc=526');
  
  console.log(myURL.searchParams.get('abc'));

  Output:

  123

• urlSearchParams.getAll(name): Returns all the value of the name-value pair that matches with the argument passed. If no such pair exists, null is returned.

  const myURL = new URL(
    'https://example.org/?abc=123&abc=526');
  console.log(myURL.searchParams.getAll('abc'));

  Output:

  [ '123', '526' ]

• urlSearchParams.has(name): Returns true if the argument passed matches with any existing name of the name-value pair else returns false.

  const myURL = new URL(
    'https://example.org/?abc=123&xyz=526');
  console.log(myURL.searchParams.has('abc'));
  console.log(myURL.searchParams.has('pqr'));

  Output:

  true
  false

Manipulating the URL query:

• urlSearchParams.set(name, value): Sets the value in the URLSearchParams object associated with name to the specified value. If more than one name-value pairs exists, whose names are same as the ‘name’ argument, then the only value of first matching pair is changed, rest all are removed.

  const params = new URLSearchParams(
      'abc=123&xyz=526&abc=258');
  console.log(params.toString());
  params.set('abc', 'opq');
  console.log(params.toString());

  Output:

  abc=123&xyz=526&abc=258
  abc=opq&xyz=526

• urlSearchParams.append(name, value): Appends a new name-value pair to the existing URLSearchParams query.

  const params = new URLSearchParams('xyz=123');
  params.append('foo', '789');
  params.append('xyz', 'zoo');
  params.append('foo', 'def');
  console.log(params.toString());

  Output:

  xyz=123&foo=789&xyz=zoo&foo=def

• urlSearchParams.delete(name): Removes all name-value pairs whose name is same as ‘name’ argument.

  const params = new URLSearchParams(
    'xyz=123&foo=789&xyz=zoo&foo=def');
  console.log(params.toString());
  params.delete('foo');
  console.log(params.toString());

  Output:

  xyz=123&foo=789&xyz=zoo&foo=def
  xyz=123&xyz=zoo

• urlSearchParams.sort(): Sorts the existing name-value pairs in-place by their names using a stable sorting algorithm.

  const params = new URLSearchParams(
    'query=node&type=search&abc=programs');
  params.sort();
  console.log(params.toString());

  Output:

  abc=programs&query=node&type=search

• urlSearchParams.toString(): Returns the URL search parameters as a string, with characters percent-encoded wherever necessary.

  const params = new URLSearchParams(
    'query=node&type=search&passwd[]=3456');
  console.log(params.toString());

  Output:

  query=node&type=search&passwd%5B%5D=3456

Iterating the URL query:

• urlSearchParams.entries(): Returns an iterator over the entry set of the param object.

  const params = new URLSearchParams(
      'query=node&type=search&passwd=3456');
  for(var pair of params.entries()) {
     console.log(pair[0]+ '-->'+ pair[1]);
  }

  Output:

  query-->node
  type-->search
  passwd-->3456

• urlSearchParams.keys(): Returns an iterator over the key set of the param object.

  const params = new URLSearchParams(
      'query=node&type=search&passwd=3456');
  for(var key of params.keys()) {
     console.log(key);
  }

  Output:

  query
  type
  passwd

• urlSearchParams.values(): Returns an iterator over the value set of the param object.

  const params = new URLSearchParams(
      'query=node&type=search&passwd=3456');
  for(var value of params.values()) {
     console.log(value);
  }

  Output:

  node
  search
  3456

• urlSearchParams.forEach(fn[, arg]): fn is a function invoked for each name-value pair in the query and arg is an object to be used when ‘fn’ is called. It iterates over each name-value pair in the query and invokes the function.

  const myURL = new URL(
    'https://example.com/?a=b&c=d&d=z');
  myURL.searchParams.forEach(
    (value, name, searchParams) => {
  console.log(name, value,
    myURL.searchParams === searchParams);
  });

  Output:

  a b true
  c d true
  d z true

• urlSearchParams[Symbol.iterator]():

  const params=new URLSearchParams(
      'firstname=john&lastname=beck&gender=male');
  for (const [name, value] of params) {
    console.log(name, value);
  }

  Output:

  firstname john
  lastname beck
  gender male