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Table of contents
1.
Introduction
2.
Why This Function is Used
3.
Syntax, Parameter and Return Value
3.1.
Syntax:
3.2.
Parameters:
3.3.
Return Value: 
4.
Examples 
4.1.
Basic Delayed Function Execution:
4.2.
JavaScript
4.3.
Delaying a Task with Multiple Arguments:
4.4.
JavaScript
4.5.
Using Delay for Throttling Behavior:
4.6.
JavaScript
4.7.
Scheduling Multiple Delayed Calls:
4.8.
JavaScript
5.
Frequently Asked Questions 
5.1.
How does _.delay() differ from the native setTimeout?
5.2.
Can the delay be cancelled once set with _.delay()?
5.3.
Is _.delay() appropriate for time-sensitive applications?
6.
Conclusion
Last Updated: Mar 27, 2024
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Lodash _.delay() Method

Author Rinki Deka
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Introduction

Timing control is a crucial aspect of JavaScript programming, particularly when scheduling functions to run after a specific delay. Lodash enhances this functionality with the _.delay() method. This function is similar to JavaScript's native setTimeout, but with a more flexible syntax and additional capabilities. It allows you to delay the execution of a function by a specified number of milliseconds. 

Lodash _.delay() Method

This article will cover the _.delay() method, highlighting its syntax, use cases, and benefits, supported by examples and FAQs.

Why This Function is Used

The _.delay() function is used to postpone the execution of a function until after a specified period. This can be particularly useful in scenarios like debouncing user input, delaying actions until certain conditions are met, or simply scheduling tasks to run after a set interval. It offers a more readable and convenient way to handle time-based function execution compared to the native setTimeout.

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Syntax, Parameter and Return Value

Syntax:

 _.delay(func, wait, [...args])

Parameters:

  • func (Function): The function to delay.
     
  • wait (number): The number of milliseconds to delay invocation.
     
  • [...args]: The arguments to invoke the function with.

Return Value: 

(number) - Returns the timer ID which can be used to cancel the delay.

Examples 

Basic Delayed Function Execution:

  • JavaScript

JavaScript

var _ = require('lodash');

function greet(name) {

 console.log('Hello, ' + name);

}

_.delay(greet, 1000, 'John');

 Output after 1 second:

'Hello, John'


Demonstrates delaying a greeting function by 1 second.

Delaying a Task with Multiple Arguments:

  • JavaScript

JavaScript

function logEvent(eventType, message) {

 console.log(eventType + ': ' + message);

}

_.delay(logEvent, 2000, 'UserLogin', 'User logged in successfully');

 Output after 2 seconds: 

'UserLogin: User logged in successfully'


Shows delaying a function with multiple arguments.

Using Delay for Throttling Behavior:

  • JavaScript

JavaScript

var saveData = function(data) {

 console.log('Data saved:', data);

};

document.getElementById('saveButton').addEventListener('click', () => {

 _.delay(saveData, 500, 'User data');

});

// Delays the saveData function by 500ms on button click.

An example of using _.delay() to throttle a button click handler.

Scheduling Multiple Delayed Calls:

  • JavaScript

JavaScript

function reminder(message) {

 console.log(message);

}

_.delay(reminder, 1000, 'Reminder 1');

_.delay(reminder, 3000, 'Reminder 2');

Output after 1 second:

 'Reminder 1'


Output after 3 seconds:

 'Reminder 2'


Demonstrates scheduling multiple functions with different delays.

Frequently Asked Questions 

How does _.delay() differ from the native setTimeout?

_.delay() offers a syntax that is more aligned with functional programming and is more readable, especially when dealing with multiple arguments for the delayed function.

Can the delay be cancelled once set with _.delay()?

Yes, the delay can be cancelled using clearTimeout, as _.delay() returns a timer ID similar to setTimeout.

Is _.delay() appropriate for time-sensitive applications?

While useful for basic timing needs, _.delay(), like setTimeout, is not guaranteed to execute precisely at the specified time due to JavaScript's single-threaded nature and event loop behavior.

Conclusion

Lodash's _.delay() method is a convenient and readable way to handle delayed function execution, offering enhanced syntax and functionality over the native setTimeout. It's especially useful for scheduling tasks, throttling event handlers, or simply delaying function calls.

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