window.onbeforeunload = function (e) {
 e = e || window.event;
 
 // 兼容IE8和Firefox 4之前的版本
 if (e) {
 e.returnValue = '关闭提示';
 }
 
 // Chrome, Safari, Firefox 4+, Opera 12+ , IE 9+
 return '关闭提示';
};

methods: {
 beforeunloadHandler (e) {
 // ...
 }
}

mounted() {
 window.addEventListener('beforeunload', e => this.beforeunloadHandler(e))
}

destroyed() {
 window.removeEventListener('beforeunload', e => this.beforeunloadHandler(e))
}