突出显示混合2段的文本范围

Question

<p class="can-select">these are para1 and para2</p>

<p class="can-select">         
   <span>these are</span>
   <span>para1</span>
   <span>and</span>
  <span>para2</span>
</p>

如何在一般情况下选择并“突出显示”文字“是para1和para2”。