


debounce
For high energy consumption events, the debounce function is a good solution. If you don't use the debounce function for scroll, resize, and key* events, then you are almost making a mistake. The following debounce function can keep your code efficient:
// 返回一个函数,如果它被不间断地调用,它将不会得到执行。该函数在停止调用 N 毫秒后,再次调用它才会得到执行。如果有传递 ‘immediate' 参数,会马上将函数安排到执行队列中,而不会延迟。 function debounce(func, wait, immediate) { var timeout; return function() { var context = this, args = arguments; var later = function() { timeout = null; if (!immediate) func.apply(context, args); }; var callNow = immediate && !timeout; clearTimeout(timeout); timeout = setTimeout(later, wait); if (callNow) func.apply(context, args); }; }; // 用法 var myEfficientFn = debounce(function() { // 所有繁重的操作 }, 250); window.addEventListener('resize', myEfficientFn);
The debounce function does not allow the callback function to be executed more than once within a specified time. This function is particularly important when assigning a callback function to an event that will be triggered frequently.
poll
Although the debounce function is mentioned above, you cannot insert an event to determine the required state if the event does not exist. Then you need to check whether the status meets your requirements every once in a while.
function poll(fn, callback, errback, timeout, interval) { var endTime = Number(new Date()) + (timeout || 2000); interval = interval || 100; (function p() { // 如果条件满足,则执行! if(fn()) { callback(); } // 如果条件不满足,但并未超时,再来一次 else if (Number(new Date()) < endTime) { setTimeout(p, interval); } // 不匹配且时间消耗过长,则拒绝! else { errback(new Error('timed out for ' + fn + ': ' + arguments)); } })(); } // 用法:确保元素可见 poll( function() { return document.getElementById('lightbox').offsetWidth > 0; }, function() { // 执行,成功的回调函数 }, function() { // 错误,失败的回调函数 } );
Polling has been used in the web for a long time and will still be used in the future.
once
Sometimes, you want a given function to occur only once, similar to the onload event. The code below provides the functionality you are talking about:
function once(fn, context) { var result; return function() { if(fn) { result = fn.apply(context || this, arguments); fn = null; } return result; }; } // 用法 var canOnlyFireOnce = once(function() { console.log('Fired!'); }); canOnlyFireOnce(); // "Fired!" canOnlyFireOnce(); // nada // 没有执行指定函数
once functions ensure that a given function can only be called once, thus preventing repeated initialization!
The above is the detailed content of Detailed explanation of the usage of basic JavaScript functions debounce, poll and once instances. For more information, please follow other related articles on the PHP Chinese website!

去掉重复并排序的方法:1、使用“Array.from(new Set(arr))”或者“[…new Set(arr)]”语句,去掉数组中的重复元素,返回去重后的新数组;2、利用sort()对去重数组进行排序,语法“去重数组.sort()”。

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于Symbol类型、隐藏属性及全局注册表的相关问题,包括了Symbol类型的描述、Symbol不会隐式转字符串等问题,下面一起来看一下,希望对大家有帮助。

怎么制作文字轮播与图片轮播?大家第一想到的是不是利用js,其实利用纯CSS也能实现文字轮播与图片轮播,下面来看看实现方法,希望对大家有所帮助!

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于对象的构造函数和new操作符,构造函数是所有对象的成员方法中,最早被调用的那个,下面一起来看一下吧,希望对大家有帮助。

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于面向对象的相关问题,包括了属性描述符、数据描述符、存取描述符等等内容,下面一起来看一下,希望对大家有帮助。

方法:1、利用“点击元素对象.unbind("click");”方法,该方法可以移除被选元素的事件处理程序;2、利用“点击元素对象.off("click");”方法,该方法可以移除通过on()方法添加的事件处理程序。

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于BOM操作的相关问题,包括了window对象的常见事件、JavaScript执行机制等等相关内容,下面一起来看一下,希望对大家有帮助。

foreach不是es6的方法。foreach是es3中一个遍历数组的方法,可以调用数组的每个元素,并将元素传给回调函数进行处理,语法“array.forEach(function(当前元素,索引,数组){...})”;该方法不处理空数组。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

Dreamweaver Mac version
Visual web development tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

SublimeText3 Mac version
God-level code editing software (SublimeText3)

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
