Lodash _.constant() Method

Syntax, Parameter and Return Value

Syntax:

 _.constant(value)

Parameters:

value: The value to return from the created function.

Return Value: 

(Function) - Returns the new constant function.

Examples 

Creating a Constant Function:

• JavaScript

JavaScript

var _ = require('lodash');

var getFive = _.constant(5);

console.log(getFive());

You can also try this code with Online Javascript Compiler

Run Code

Output:

 5

Demonstrates creating a function that always returns the number 5.

Using as a Default Function in Higher-Order Operations:

• JavaScript

JavaScript

var defaultValue = _.constant('default');

var result = _.map([1, null, 3], item => item || defaultValue());

console.log(result);

You can also try this code with Online Javascript Compiler

Run Code

Output: 

[1, 'default', 3]

Shows using a constant function to provide default values in a map operation.

Setting a Constant Callback:

var constantCallback = _.constant('Callback Result');
someAsyncFunction(constantCallback);

You can also try this code with Online Javascript Compiler

Run Code

// 'constantCallback' will always return 'Callback Result' when invoked

An example of using a constant function as a callback that returns a fixed value.

Simplifying Default Parameters:

• JavaScript

JavaScript

var getDefaultMessage = _.constant('No message available');

function logMessage(message) {

  message = message || getDefaultMessage();

  console.log(message);

}

logMessage();

You can also try this code with Online Javascript Compiler

Run Code

Output:

 'No message available'

Demonstrates setting a default parameter value using a constant function.

Frequently Asked Questions

How does _.constant() differ from using a regular function?

_.constant() provides a concise way to create a function for a constant value without manually defining a new function each time. It's a shorthand for a common pattern in functional programming.

Can _.constant() return functions or objects?

Yes, the value returned by _.constant() can be any type, including objects, arrays, or even other functions.

Is _.constant() commonly used in real-world applications?

_.constant() is especially useful in functional programming, configuration settings, and scenarios where a fixed value needs to be returned consistently.

Conclusion

Lodash's _.constant() method is a handy tool for creating functions that always return a fixed value. It's useful for default values, callbacks, and maintaining consistency in functional programming patterns.

You can refer to our guided paths on the Coding Ninjas. You can check our course to learn more about DSA, DBMS, Competitive Programming, Python, Java, JavaScript, etc. 

Also, check out some of the Guided Paths on topics such as Data Structure and Algorithms, Competitive Programming, Operating Systems, Computer Networks, DBMS, System Design, etc., as well as some Contests, Test Series, and Interview Experiences curated by top Industry Experts.