Summary of DOM size measurement and throttling techniques in JavaScript

Preface

When developing web pages, we often need to obtain the width and height of elements, or handle some events such as scrolling and window adjustment. However, frequent triggering of these events may affect page performance if not optimized. Today's article will introduce how to obtain the size of DOM elements through JavaScript, and also talk about how to use Throttle to optimize high-frequency event processing to make your web page run smoother.

1. How to get the size of the element

JavaScript provides many methods to obtain the width and height of elements, and the following are some commonly used ones.

1. and

• clientHeight: Returns the element'shigh,includepadding, but not includingborder、marginand scrollbar.
• clientWidth: Returns the element'swidth, logic andclientHeightSimilar.

These properties are very suitable for getting elementsActual visible area, for example, you need to know how much space an element takes up on the page.

// Get the height of the browser viewportlet viewportHeight = ;

// Get the width of an elementlet elementWidth = ('.my-element').clientWidth;

2. and

These two attributes represent the element'sTotal heightandTotal width, including those that are beyond the visual range, suitable for elements with scroll bars.

// Get the total height of the pagelet pageHeight = ;

// Get the total width of a scrolling arealet elementScrollWidth = ('.scrollable-element').scrollWidth;

3. and

• scrollTop: Indicates how many pixels have been scrolled down.
• scrollLeft: Indicates how many pixels have been scrolled to the right.

These two properties are often used to listen for scrolling events, such as triggering more content when the user scrolls to a certain position.

// Get the vertical distance of the current page scrollinglet scrollTop = ;

2. Throttle and anti-shake (Debounce)

In development, events like scrolling and window adjustments are sometimes triggered very frequently. If you perform some time-consuming operation every time the event is triggered, the page may become very stuck. We can useThrottleandAnti-shaketo optimize these operations.

1. Throttle

The purpose of throttling is to make a function only execute once within a fixed time. No matter how many times the event is fired during this time period, the function will only be executed once within the time interval.

function throttle(fn, delay) {
  let valid = true;
  return function() {
    if (!valid) {
      return;
    }
    valid = false;
    setTimeout(() => {
      fn();
      valid = true;
    }, delay);
  };
}

// Example: Print the position of the scroll bar every 300 millisecondsfunction showScrollPosition() {
  let scrollTop = ;
  ('Scrollbar position:' + scrollTop);
}

 = throttle(showScrollPosition, 300);

2. Application scenarios for throttling and anti-shake

• Search box: When the user enters in the search box, use throttling to reduce excessively frequent requests, such as sending a request every 500 milliseconds.
• Window adjustment (resize): When the page is resized, we usually only want to perform an operation once after the user stops adjusting, and at this time we can use anti-shake.

Summarize

Today, we get the size of DOM elements through JavaScript and use Throttle to optimize the content of high-frequency event processing.

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