SOURCE

// 防抖
function debounce(fn, wait = 50, immediate) {
	let timer;
	return function() {
		if (immediate) {
			fn.apply(this, arguments)
		}
        if (timer) clearTimeout(timer)

        timer = setTimeout(() => {
			fn.apply(this, arguments)
		}, wait)
	}
}

// 节流
function throttle(fn, wait) {
	let prev = new Date();
	return function() {
		const args = arguments;
		const now = new Date();
		if (now - prev > wait) {
			fn.apply(this, args);
			prev = new Date()
		}
    }
}