根据值更改i标签的css

Question

我将如何迭代类名student-week-diff，如果该值小于或大于0，则将该类从student-week-diff更改为fa-level-up（如果大于0）和fa-level-down（如果小于0）

这是我的html表，我已经定义了一个类名为student-week-diff

<table class="table table-hover" id="studentweek">
    <thead>
        <tr>
            <th>Year</th>
            <th>Weeks</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>VAR (%)</td>
            <td class="text-warning"> <i class="student-week-diff">-10.65%</i></td>
        </tr>
        <tr>
            <td>VAR (diff)</td>
            <td class="text-warning"> <i class="student-week-diff">-13,953</i></td>
        </tr>
        <tr>
            <td>VAR (%)</td>
            <td class="text-navy"> <i class="student-week-diff">8.81%</i></td>
        </tr>
        <tr>
            <td>VAR (diff)</td>
            <td class="text-navy"> <i class="student-week-diff">11,320</i></td>
        </tr>
    </tbody>
</table>

这是我的踪迹

var test = $(parseFloat('.student-week-diff').text());

$.each (test, function(){
    if (test < 0) {
        $('.student-week-diff').removeClass(".student-week-diff").addClass(".fa-level-down");
    } else {
        $('.student-week-diff').removeClass('.student-week-diff').addClass(".fa-level-up");
    }
});