Hemendra Khatik
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What is throttling in JavaScript?

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Hemendra Khatik
·Jul 1, 2022·

2 min read

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Again a jargonish word, but let me demystify it for you.

let me help you

It's nothing but a simple technique we use to prevent unnecessary function calls to improve app's performance.

Unlike Debouncing, here we block a function call for a particular time if it's been executed recently. Or we could also say that throttling ensures a function call regularly at a fixed rate.

Let's look at the below example,

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Throttling</title>
    </head>
    <body>
        <button class="btn">Click here</button>
        <script src="index.js"></script>
    </body>
</html>
let count = 0;
function submitData(query){
   // some api call
   console.log("result",count++)
}

document.querySelector(".btn").addEventListener("click",()=>{
submitData();
})

first example

In the above example, if you click 10 times in 2000ms, Function will be called 10 times, as you can clearly see in the above example.

It's a very expensive operation, and as dev, our job is to make operations as cheap as possible.

Let's see how throttling helps us to make these operations cheaper.

function throttle(fn,delay){
  let last = 0;
 /*  
here ...args is optional I've used this in case, if you 
want to pass some parameters you can use ...args
*/ 
  return (...args)=>{
    const now = new Date().getTime();
    if(now - last < delay){
      return;
    }
   last = now;
   return fn(...args)
  }

}

const magicFunction = throttle(submitData,1000);

let count = 0;
function submitData(){
   // some api call
   console.log("result",count++)
}

document.querySelector(".btn").addEventListener("click",magicFunction);

second

Now, if you click 10 times in 2000ms, Function will be called 2 times only, as you can see in the code. We have blocked the function call for 1000ms.

That's how we can implement the throttling technique to improve our app's performance


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