Home Web Front-end JS Tutorial When to Use Parentheses with JavaScript Function References?

When to Use Parentheses with JavaScript Function References?

Dec 05, 2024 am 10:27 AM

When to Use Parentheses with JavaScript Function References?

When to Use Parentheses and When Not?

In JavaScript, it's crucial to understand when to use parentheses and when not, particularly with function references. Consider the following code:

var myFunction = function() {
   setTimeout(myFunction, 1000);
}
myFunction();
Copy after login

Why does the function call in setTimeout not require parentheses, while the last line does?

Nutshell

  • myFunction references the function
  • myFunction() calls the function

Detailed Explanation

setTimeout accepts a function reference as an argument. In the first line, setTimeout(myFunction, 1000) passes the function reference without parentheses because it expects a reference.

However, in the last line, myFunction() is actually calling the function. To invoke a function, we use parentheses to execute it. Hence, myFunction() executes the function and therefore requires parentheses.

Exception

There may be instances where setTimeout(myFunction(), 1000) is appropriate, such as when myFunction() returns a function. For example:

function myFunction() {
    return function() {
        alert("ohai")
    }
}

// Or

const myFunction = () => () => alert("ohai")
Copy after login

In this case, setTimeout(myFunction(), 1000):

  • Calls the outer function myFunction
  • Obtains the return value, which is an inner function
  • Passes the inner function as the argument to setTimeout

This results in an alert every second.

Conclusion

Understanding the purpose of parentheses in function references is essential for effective JavaScript programming. By remembering that parentheses indicate a function call, you can correctly use them to invoke functions or pass function references as needed.

The above is the detailed content of When to Use Parentheses with JavaScript Function References?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

What should I do if I encounter garbled code printing for front-end thermal paper receipts? What should I do if I encounter garbled code printing for front-end thermal paper receipts? Apr 04, 2025 pm 02:42 PM

Frequently Asked Questions and Solutions for Front-end Thermal Paper Ticket Printing In Front-end Development, Ticket Printing is a common requirement. However, many developers are implementing...

Demystifying JavaScript: What It Does and Why It Matters Demystifying JavaScript: What It Does and Why It Matters Apr 09, 2025 am 12:07 AM

JavaScript is the cornerstone of modern web development, and its main functions include event-driven programming, dynamic content generation and asynchronous programming. 1) Event-driven programming allows web pages to change dynamically according to user operations. 2) Dynamic content generation allows page content to be adjusted according to conditions. 3) Asynchronous programming ensures that the user interface is not blocked. JavaScript is widely used in web interaction, single-page application and server-side development, greatly improving the flexibility of user experience and cross-platform development.

Who gets paid more Python or JavaScript? Who gets paid more Python or JavaScript? Apr 04, 2025 am 12:09 AM

There is no absolute salary for Python and JavaScript developers, depending on skills and industry needs. 1. Python may be paid more in data science and machine learning. 2. JavaScript has great demand in front-end and full-stack development, and its salary is also considerable. 3. Influencing factors include experience, geographical location, company size and specific skills.

How to achieve parallax scrolling and element animation effects, like Shiseido's official website?
or:
How can we achieve the animation effect accompanied by page scrolling like Shiseido's official website? How to achieve parallax scrolling and element animation effects, like Shiseido's official website? or: How can we achieve the animation effect accompanied by page scrolling like Shiseido's official website? Apr 04, 2025 pm 05:36 PM

Discussion on the realization of parallax scrolling and element animation effects in this article will explore how to achieve similar to Shiseido official website (https://www.shiseido.co.jp/sb/wonderland/)...

Is JavaScript hard to learn? Is JavaScript hard to learn? Apr 03, 2025 am 12:20 AM

Learning JavaScript is not difficult, but it is challenging. 1) Understand basic concepts such as variables, data types, functions, etc. 2) Master asynchronous programming and implement it through event loops. 3) Use DOM operations and Promise to handle asynchronous requests. 4) Avoid common mistakes and use debugging techniques. 5) Optimize performance and follow best practices.

The Evolution of JavaScript: Current Trends and Future Prospects The Evolution of JavaScript: Current Trends and Future Prospects Apr 10, 2025 am 09:33 AM

The latest trends in JavaScript include the rise of TypeScript, the popularity of modern frameworks and libraries, and the application of WebAssembly. Future prospects cover more powerful type systems, the development of server-side JavaScript, the expansion of artificial intelligence and machine learning, and the potential of IoT and edge computing.

How to merge array elements with the same ID into one object using JavaScript? How to merge array elements with the same ID into one object using JavaScript? Apr 04, 2025 pm 05:09 PM

How to merge array elements with the same ID into one object in JavaScript? When processing data, we often encounter the need to have the same ID...

Zustand asynchronous operation: How to ensure the latest state obtained by useStore? Zustand asynchronous operation: How to ensure the latest state obtained by useStore? Apr 04, 2025 pm 02:09 PM

Data update problems in zustand asynchronous operations. When using the zustand state management library, you often encounter the problem of data updates that cause asynchronous operations to be untimely. �...

See all articles