JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<div class="add">
    <input id="file" type="file" ng2FileSelect [uploader]="uploader">
    <label class="btn btn-primary" for="file">
        <i class="fa fa-book"></i><span>Add a book</span>
    </label>
</div>
<div class="controls">
    <button type="button" class="btn btn-primary" (click)="uploader.uploadAll()" [disabled]="!uploader.getNotUploadedItems().length"
    style="display: inline-block;">
        <i class="fa fa-cloud-upload"></i><span>Upload all</span>
    </button>
</div>

CSS

.btn {
  display: inline-flex;
  align-items: center;
  min-height: 30px;
  padding: 0 10px;
  border: 1px solid;
  border-radius: 2px;
  font-family: 'Roboto', sans-serif;
  font-size: 14px;
  cursor: pointer;
  > .fa {
    margin-right: 5px;
  }
  &:disabled {
    background-color: $color-bg;
    border-color: $color-bg;
    color: $color-text;
    cursor: not-allowed;
  }
}