JavaScript 节流与防抖函数实现及测试详解

节流函数原理与实现

节流（Throttle）的主要作用是忽略特定时间窗口内的重复调用，适用于触发频率较高且处理逻辑较为沉重的场景。

 
var throttle = function (func, threshold, alt) {
var last = Date.now();
threshold = threshold || 100;
return function () {
var now = Date.now();
if (now - last < threshold) {
if (alt) {
alt.apply(this, arguments);
} 
return;
} 
last = now;
func.apply(this, arguments);
}; 
}; 

防抖函数原理与实现

当处于设定的时间间隔内未发生新调用时，才会执行被调用的方法。

 
var debounce = function (func, threshold, execASAP) {
var timeout = null;
threshold = threshold || 100;
return function () {
var self = this;
var args = arguments;
var delayed = function () {
if (!execASAP) {
func.apply(self, args);
} 
timeout = null;
}; 
if (timeout) {
clearTimeout(timeout);
} else if (execASAP) {
func.apply(self, args);
} 
timeout = setTimeout(delayed, threshold);
}; 
}; 

 
var test = function (wrapper, threshold) {
var log = function () {
console.log(Date.now() - start);
}; 
var wrapperedFunc = wrapper(log, threshold);
var start = Date.now();
var arr = [];
for (var i = 0; i < 10; i++) {
arr.push(wrapperedFunc);
} 
while(i > 0) {
var random = Math.random() * 1000;
console.log('index: ' + i);
console.log('random: ' + random);
setTimeout(arr[--i], random);
} 
}; 
test(debounce, 1000);
test(throttle, 1000);