原生JS设置公众号页面的title过长，类似走马灯效果

项目中经常用到的方法，放这边省的写其他项目用到了还要重新写或者翻以前项目

//title过长类似走马灯效果
function changeTitle(title) {
	//timer定时器唯一ID
	if (Vue.prototype.titletimer != null) {
		clearInterval(Vue.prototype.titletimer);
		Vue.prototype.titletimer = null
	}
	let len = title.length;//总长度
	const size = 14; //展示的title长度
	const rate = 500; //title滚动的频率，最小300ms
	if (len > size) {
		let num = 0;
		let tmpStr = title.substr(num, size);
		document.title = tmpStr;
		Vue.prototype.titletimer = setInterval(() => {
			num++;
			if (num > (len - size)) num = 0;
			let tmpTitle = title.substr(num, size);
			document.title = tmpTitle;
		}, rate < 300 ? 300 : rate);
	} else {
		document.title = title;
	}
}