React中使用防抖函数和节流函数
在React事件调用时，React传递给事件处理程序是一个合成事件对象的实例。SyntheticEvent对象是通过合并得到的。 这意味着在事件回调被调用后，SyntheticEvent 对象将被重用并且所有属性都将被取消。 这是出于性能原因。 因此，您无法以异步方式访问该事件。React合成事件官方文档
所以在用防抖或节流函数封装时，异步方式访问事件对象出现问题。解决的方法如下：
方法一：调用合成事件对象的persist()方法 event.persist && event.persist() //保留对事件的引用
方法二：深拷贝事件对象 const event = e && {...e} //深拷贝事件对象
function debounce(func, wait=500) {let timeout; // 定时器变量return function(event){clearTimeout(timeout); // 每次触发时先清除上一次的定时器,然后重新计时event.persist && event.persist() //保留对事件的引用//const event = e && {...e} //深拷贝事件对象timeout = setTimeout(()=>{func(event)}, wait); // 指定 xx ms 后触发真正想进行的操作 handler};} 防抖debounce
防抖 Debounce 多次触发，只在最后一次触发时，执行目标函数。
函数防抖就是，延迟一段时间再执行函数，如果这段时间内又触发了该函数，则延迟重新计算。
应用场景
（1）通过监听某些事件完成对应的需求，比如：
通过监听 scroll 事件，检测滚动位置，根据滚动位置显示返回顶部按钮
通过监听 resize 事件，对某些自适应页面调整DOM的渲染（通过CSS实现的自适应不再此范围内）
通过监听 keyup 事件，监听文字输入并调用接口进行模糊匹配
（2）其他场景
表单组件输入内容验证
防止多次点击导致表单多次提交
简单实现
function debounce(fn, wait) {let treturn () => {let context = thislet args = argumentsif (t) clearTimeout(t)t= setTimeout(() => {fn.apply(context, args)}, wait)}} 完整实现
function debounce(func, wait, immediate) {let time;let debounced = function() {let context = this;if(time) clearTimeout(time);if(immediate) {let callNow = !time;if(callNow) func.apply(context, arguments);time = setTimeout(()=>{time = null} //见注解, wait)} else {time = setTimeout(()=>{func.apply(context, arguments)}, wait) }};debounced.cancel = function() {clearTimeout(time);time = null};return debounced}// underscore.js debounce//// Returns a function, that, as long as it continues to be invoked, will not// be triggered. The function will be called after it stops being called for// N milliseconds. If `immediate` is passed, trigger the function on the// leading edge, instead of the trailing._.debounce = function(func, wait, immediate) {var timeout, args, context, timestamp, result;// 处理时间var later = function() {var last = _.now() - timestamp;if (last < wait && last >= 0) {timeout = setTimeout(later, wait - last); // 10ms 6ms 4ms} else {timeout = null;if (!immediate) {result = func.apply(context, args);if (!timeout) context = args = null;}}}; react中调用方法
this.handleGetCustomerNameList = debounce(this.handleGetCustomerNameList.bind(this), 500);
节流 throttle
节流：函数间隔一段时间后才能再触发，避免某些函数触发频率过高，比如滚动条滚动事件触发的函数。
### 简单实现function throttle (fn, wait, mustRun) {let start = new Date()let timeoutreturn () => {// 在返回的函数内部保留上下文和参数let context = thislet args = argumentslet current = new Date()clearTimeout(timeout)let remaining = current - start// 达到了指定触发时间，触发该函数if (remaining > mustRun) {fn.apply(context, args)start = current} else {// 否则wait时间后触发，闭包保留一个timeout实例timeout = setTimeout(fn, wait);}}} 完整实现
function throttle(func, wait, options) {let time, context, args, result;let previous = 0;if (!options) options = {};let later = function () {previous = options.leading === false ? 0 : new Date().getTime();time = null;func.apply(context, args);if (!time) context = args = null;};let throttled = function () {let now = new Date().getTime();if (!previous && options.leading === false) previous = now;let remaining = wait - (now - previous);context = this;args = arguments;if (remaining <= 0 || remaining > wait) {if (time) {clearTimeout(time);time = null;}previous = now;func.apply(context, args);if (!time) context = args = null;} else if (!time && options.trailing !== false) {time = setTimeout(later, remaining);}};return throttled;}// underscore.js throttle// Returns a function, that, when invoked, will only be triggered at most once// during a given window of time. Normally, the throttled function will run// as much as it can, without ever going more than once per `wait` duration;// but if you'd like to disable the execution on the leading edge, pass// `{leading: false}`. To disable execution on the trailing edge, ditto._.throttle = function(func, wait, options) {var context, args, result;var timeout = null;var previous = 0;if (!options) options = {};var later = function() {previous = options.leading === false ? 0 : _.now();timeout = null;result = func.apply(context, args);if (!timeout) context = args = null;};return function() {var now = _.now();if (!previous && options.leading === false) previous = now;var remaining = wait - (now - previous);context = this;args = arguments;if (remaining <= 0 || remaining > wait) {if (timeout) {clearTimeout(timeout);timeout = null;}previous = now;result = func.apply(context, args);if (!timeout) context = args = null;} else if (!timeout && options.trailing !== false) {timeout = setTimeout(later, remaining);}return result;};}; react中调用方法
this.handleGetCustomerNameList = throttle (this.handleGetCustomerNameList.bind(this), 500);
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持VeVb武林网。
注：相关教程知识阅读请移步到JavaScript/Ajax教程频道。
