JavaScript:void Tips: Improve website performance

The void operator in JavaScript improves website performance by deferring resource-intensive operations. Usage scenarios include: deferring DOM queries, time-consuming function calls, and dynamic element loading. Care needs to be taken to ensure that only operations that need to be delayed are delayed and the returned undefined value is properly handled.

JavaScript: void Tips: Improve website performance

void operator is a JavaScript A less common operator that takes an expression and returns undefined. The seemingly useless void can actually be cleverly used to optimize website performance.

How to use void to improve performance

When you perform certain resource-intensive operations in JavaScript code (such as DOM queries or time-consuming function calls), you can Use the void operator to defer execution of this operation until needed.

For example, in the following code:

const elements = document.querySelectorAll('li');

querySelectorAll() method is a resource-intensive operation that synchronously queries all matching elements in the DOM. You can defer doing this until the elements are actually needed by using void:

const elementsPromise = void document.querySelectorAll('li');

At this point, the elements array will only be used if it is actually needed. Perform the querySelectorAll() operation. This means that page loading speed is not affected by query latency.

Practical Case

Suppose you have a complex user interface that contains a large number of dynamic DOM elements. To load these elements as the user scrolls, you can use the following code:

window.addEventListener('scroll', () => {
  if (shouldLoadElements) {
    const elementsPromise = void document.querySelectorAll('.dynamic-elements');
    elementsPromise.then(elements => {
      // 处理动态元素
    });
  }
});

In this example, the querySelectorAll() operation is not performed immediately, but is deferred until the dynamic elements need to be processed . This helps optimize page loading and prevents stuttering when scrolling.

Notes

Be careful when using the void operator to optimize performance:

• Ensure that only delays are required operation.
• Properly handle the void returned undefined value.
• Because the void operator forces a synchronous operation to be converted to an asynchronous operation, it may cause problems in some situations where synchronous execution is required.

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