This could probably be better as

```javascript
if (this.order !== 'user_asc') {
    this.order = 'user_asc'
} else {
    this.order = 'user_desc';
}
```

or more succinctly
```javascript
this.order = (this.order !== 'user_asc') ? 'user_asc' : 'user_desc';
```