Syntax, Parameter and Return Value
Syntax:
_.defer(func, [...args])
Parameters:
-
func (Function): The function to defer.
- [...args]: The arguments to invoke the function with.
Return Value:
(number) - Returns the timer ID for cancelling the deferred function (similar to setTimeout).
Examples
Deferring a Simple Function:
JavaScript
var _ = require('lodash');
function greet(name) {
console.log('Hello, ' + name);
}
_.defer(greet, 'John');
You can also try this code with Online Javascript Compiler
Output (after the current call stack clears):
'Hello, John'
Demonstrates deferring a simple greeting function.
Updating UI After Initial Load:
JavaScript
function updateUI() {
console.log('UI updated');
}
_.defer(updateUI);
You can also try this code with Online Javascript Compiler
// UI update code will execute after the current call stack, such as initial page load, is complete.
Shows deferring a UI update function until after the page has loaded.
Deferring Function with Multiple Arguments:
JavaScript
function logDetails(a, b, c) {
console.log(a, b, c);
}
_.defer(logDetails, 'apple', 'banana', 'cherry');
You can also try this code with Online Javascript Compiler
Output:
'apple banana cherry' (deferred execution)
An example of deferring a function that takes multiple arguments.
Using Defer in Event Handlers:
JavaScript
document.getElementById('myButton').addEventListener('click', () => {
_.defer(() => console.log('Button clicked'));
});
You can also try this code with Online Javascript Compiler
// The message 'Button clicked' will be logged after the click event handling is complete.
Demonstrates using _.defer() within an event handler for post-processing.
Frequently Asked Questions
How does _.defer() differ from setTimeout(func, 0)?
_.defer() is similar to setTimeout(func, 0) but is more concise and readable. It's specifically designed for deferring function execution, making code intentions clearer.
Can the deferred function be cancelled?
Yes, the returned timer ID from _.defer() can be used with clearTimeout to cancel the deferred function before it executes.
Is _.defer() suitable for heavy computational tasks?
While _.defer() is useful for delaying tasks, heavy computations might still block the UI thread. For such tasks, Web Workers or breaking the task into smaller chunks may be more appropriate.
Conclusion
Lodash's _.defer() method provides a simple and effective way to postpone function execution until after the current call stack is cleared. It's particularly useful for deferring tasks that need to run after the immediate execution flow, such as UI updates or post-processing operations.
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.
84+ registered 