// 节流 (N秒内触发一次)
			throttle(fn, interval) {
				let last = 0
				return function () {
					let context = this
					let args = arguments
					let now = +new Date()
					if ((now - last) > interval) {
						last = now
						fn.apply(context, args)
					}
				}
			},
// 防抖(最后N秒后触发)
			debounce(fn, delay) {
				let timer = null
				return function () {
					let context = this
					let args = arguments
					if (timer) {
						clearTimeout(timer)
					}
					timer = setTimeout(() => {
						fn.apply(context, args)
					}, delay)
				}
			},
// 整合防抖和节流
			betterDebounce(fn, delay) {
				let last = 0
				let  timer = null
				return function () {
					let context = this
					let args = arguments
					let now = +new Date();
					if ((now -last) < delay) {
						clearTimeout(timer)
						timer = setTimeout( () => {
							fn.apply(context, args)
							last = now
						}, delay)
					} else {
						last = now;
						fn.apply(context, args)
					}
				}
			},