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How do find out all elements that match a specific condition in JavaScript?

Javascript Web Development Front End Technology

In JavaScript, there are multiple ways to find elements that match specific conditions. While the underscore.js library provides the _.where() function, modern JavaScript also offers native methods like filter(), every(), and find().

Using _.where() from Underscore.js

The _.where() function belongs to underscore.js, a JavaScript library that provides utility functions. It finds elements that match specified properties in an array of objects.

Syntax

_.where(list, properties)

Parameters:

list ? The array to search through
properties ? Object containing the matching criteria

Return value: An array containing all elements that match the specified properties.

Example 1: Finding Users by Property

<!DOCTYPE html>
<html>
<head>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>
</head>
<body>
   <div id="result1"></div>
   <script type="text/javascript">
      var users = [
         { name: "priya", active: "false" },
         { name: "aishwarya", active: "true" },
         { name: "akanksha", active: "true" },
         { name: "ruby", active: "true" }
      ];
      
      var activeUsers = _.where(users, { active: "true" });
      document.getElementById("result1").innerHTML = JSON.stringify(activeUsers, null, 2);
   </script>
</body>
</html>

[
  {
    "name": "aishwarya",
    "active": "true"
  },
  {
    "name": "akanksha", 
    "active": "true"
  },
  {
    "name": "ruby",
    "active": "true"
  }
]

Example 2: Finding Cities by State

<!DOCTYPE html>
<html>
<head>
   <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>
</head>
<body>
   <div id="result2"></div>
   <script type="text/javascript">
      var details = [
         { "city": "Ranchi", "state": "Jharkhand", "id": "1" },
         { "city": "Jamshedpur", "state": "Jharkhand", "id": "2" },
         { "city": "Hyderabad", "state": "Telangana", "id": "3" },
         { "city": "Delhi", "state": "Delhi", "id": "4" },
         { "city": "Pune", "state": "Maharashtra", "id": "5" }
      ];
      
      var jharkhandCities = _.where(details, {state: "Jharkhand"});
      document.getElementById("result2").innerHTML = JSON.stringify(jharkhandCities, null, 2);
   </script>
</body>
</html>

[
  {
    "city": "Ranchi",
    "state": "Jharkhand",
    "id": "1"
  },
  {
    "city": "Jamshedpur",
    "state": "Jharkhand", 
    "id": "2"
  }
]

Using Native JavaScript Array.filter()

Modern JavaScript provides the filter() method for finding elements that match conditions.

<!DOCTYPE html>
<html>
<body>
   <div id="result3"></div>
   <script>
      let users = [
         { id: 1, name: "priya", age: 25 },
         { id: 2, name: "aishwarya", age: 30 },
         { id: 3, name: "akanksha", age: 22 },
         { id: 4, name: "ruby", age: 35 }
      ];
      
      // Find users older than 25
      let olderUsers = users.filter(user => user.age > 25);
      document.getElementById("result3").innerHTML = JSON.stringify(olderUsers, null, 2);
   </script>
</body>
</html>

[
  {
    "id": 2,
    "name": "aishwarya",
    "age": 30
  },
  {
    "id": 4,
    "name": "ruby",
    "age": 35
  }
]

Using Array.every() for Testing All Elements

The every() method tests whether all elements pass a condition.

<!DOCTYPE html>
<html>
<body>
   <div id="result4"></div>
   <script>
      let numbers = [2, 4, 6, 8, 10];
      
      let allEven = numbers.every(num => num % 2 === 0);
      document.getElementById("result4").innerHTML = 
         "All numbers are even: " + allEven;
   </script>
</body>
</html>

All numbers are even: true

Comparison of Methods

Method	Returns	Use Case	Dependency
`_.where()`	Array of matching objects	Object property matching	Underscore.js
`Array.filter()`	Array of matching elements	Custom conditions	Native JavaScript
`Array.every()`	Boolean (true/false)	Test if all elements match	Native JavaScript

Conclusion

While _.where() is useful for simple object property matching, modern JavaScript's filter() method provides more flexibility and doesn't require external libraries. Choose based on your specific needs and project dependencies.

Aman Kumar

Updated on: 2026-03-15T23:19:00+05:30

1K+ Views

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