Detailed explanation of JavaScript function throttling concepts and usage examples-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

Detailed explanation of JavaScript function throttling concepts and usage examples

高洛峰

Dec 29, 2016 am 10:04 AM

The examples in this article describe the concept and usage of JavaScript function throttling. I share it with you for your reference. The details are as follows:

Recently when I was making a web page, I had a need to change the size of some page elements when the browser window changed, so I naturally thought of window resize. Event, so that’s what I wrote

<!DOCTYPE html>
<html>
<head>
  <title>Throttle</title>
</head>
<body>
  <script type="text/javascript">
    n=0;
    function resizehandler(){
      console.log(new Date().getTime());
      console.log(++n);
    }
    window.onresize=resizehandler;
  </script>
</body>
</html>

The function was implemented, but when I changed the size of the browser window by dragging, I looked at the console

Yes, it’s simple A drag and drop caused my resizeHandler() method to be executed 52 times. This is not the effect I want at all. In fact, the code of my resizeHandler() method is very complicated, and I even use ajax to send a request to the server. If it were a simple one Changing the window size requires calling it 52 times, which is okay.

Function throttling

In fact, my original intention is just to make some adjustments to the page after the window is resized, and the resize event of the window is not in It is triggered after resize is completed. I don't know the specific frequency, but it is called continuously until the window size no longer changes. In fact, a similar mechanism is mousemove, which is triggered repeatedly in a short period of time.

In "JavaScript Advanced Programming", there is a special function throttling to deal with this problem

function throttle(method,context){
  clearTimeout(method.tId);
  method.tId=setTimeout(function(){
    method.call(context);
  },500);
}

The principle is very simple. Use a timer to delay function execution by 500 milliseconds. If within 500 milliseconds, If the function is called again, the previous call will be deleted, and this call will be executed 500 milliseconds later, and so on. In this way, I can change the code I just made to

<script type="text/javascript">
n=0;
function resizehandler(){
  console.log(new Date().getTime());
  console.log(++n);
}
function throttle(method,context){
  clearTimeout(method.tId);
  method.tId=setTimeout(function(){
    method.call(context);
  },500);
}
window.onresize=function(){
  throttle(resizehandler,window);
};
</script>

and try dragging it. Sure enough, it is only executed once.

Another approach

There is also a function throttling solution on the Internet , this is how it is done

function throttle(method,delay){
  var timer=null;
  return function(){
    var context=this, args=arguments;
    clearTimeout(timer);
    timer=setTimeout(function(){
      method.apply(context,args);
    },delay);
  }
}

Try calling it, the same effect

<script type="text/javascript">
n=0;
function resizehandler(){
  console.log(new Date().getTime());
  console.log(++n);
}
function throttle(method,delay){
  var timer=null;
  return function(){
    var context=this, args=arguments;
    clearTimeout(timer);
    timer=setTimeout(function(){
      method.apply(context,args);
    },delay);
  }
}
window.onresize=throttle(resizehandler,500);//因为返回函数句柄，不用包装函数了
</script>

Detailed explanation of JavaScript function throttling concepts and usage examples

Comparison

Both methods are used Instead of setTimeout, the difference is that the function added by the second method delays the execution time. This function is easily available in the first solution, just by adding a parameter.

But the first solution sets tId as a variable of the function and saves it, while the second solution creates a closure to store it. Personally, I don't think the difference is big. I really like the first one, it's simple and efficient.

New requirements

One day I made something similar, just like the automatic prompt for input on the Baidu homepage. I bound the keyup event to the text, every time the keyboard bounces up. It prompts automatically, but I don’t want to prompt so frequently, so I used the above method, but it’s a tragedy. It only prompts after stopping input for 500 milliseconds. There is no prompt at all during the input process. I looked at the code and found that it is not true. As long as the user can touch type and press the keyboard within 500 milliseconds, the prompt function will be continuously delayed, so that the prompt will only occur when it stops, which is meaningless.

Can it be executed at a fixed interval based on function throttling?

Small changes

After searching on the Internet, we can make some changes based on the second way of writing (the first way of expanding multiple variables for functions feels a bit bad) and add a parameter as Fixed intervals must be executed

function throttle(method,delay,duration){
  var timer=null, begin=new Date();
  return function(){
    var context=this, args=arguments, current=new Date();;
    clearTimeout(timer);
    if(current-begin>=duration){
       method.apply(context,args);
       begin=current;
    }else{
      timer=setTimeout(function(){
        method.apply(context,args);
      },delay);
    }
  }
}

In this way, each time we judge how long the interval is, if it exceeds the set time, it will be executed immediately. Try the effect with the example just now

window.onresize=throttle(resizehandler,100,200);

Detailed explanation of JavaScript function throttling concepts and usage examples

Sure enough, it is neither executed frequently nor executed at the end

I hope this article will be helpful to everyone in JavaScript programming.

For more detailed explanations of JavaScript function throttling concepts and usage examples, please pay attention to the PHP Chinese website!

Statement

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

From Websites to Apps: The Diverse Applications of JavaScriptApr 22, 2025 am 12:02 AM

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python vs. JavaScript: Use Cases and Applications ComparedApr 21, 2025 am 12:01 AM

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

The Role of C/C in JavaScript Interpreters and CompilersApr 20, 2025 am 12:01 AM

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

JavaScript in Action: Real-World Examples and ProjectsApr 19, 2025 am 12:13 AM

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

JavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AM

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AM

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python vs. JavaScript: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AM

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

See all articles