vue实现快捷键

created() {
    let arr = [];
    let that = this;
    document.onkeydown = function(e) {
        if(arr.length > 0) { // a-z按键长按去重
            if(arr.indexOf(e.key.toLowerCase()) >= 0) {
                return
            }
        }
        arr.push(e.key.toLowerCase())
        this.keydown = arr.join('+');
        if(this.keydown == 'shift+enter') {
            this.keydown = '';
            that.combineFile()
        }
    }
    document.onkeyup = function (e) {
        arr.splice(arr.indexOf( e.key.toLowerCase() ),1);
        this.keydown = arr.join('+');
    }
    this.keydown = '';
}