How to set a bottom border for every row in a textarea?

Question

I am trying to figure out how to add a border-bottom line for every row within a <textarea>, however I am only able to get the very bottom row's border-bottom to do this.

Is there a way to accomplish this?

.input-borderless {
  width: 80%;
  border-top: 0px;
  border-bottom: 1px solid green;
  border-right: 0px;
  border-left: 0px;
  background-color: rgb(241,250,247);
  text-decoration: none;
  outline: none;
  display: block;
  padding: 10px 0;
  margin: 20px 0;
  font-size: 1.6em;
}

<textarea rows="3" class="input-borderless" placeholder="Describe the project"></textarea>

Answer 1

You can use gradient as the background image to get an effect that looks like underline:

JSFiddle

textarea
{
  line-height: 4ch;
  background-image: linear-gradient(transparent, transparent calc(4ch - 1px), #E7EFF8 0px);
  background-size: 100% 4ch;
}

Answer 2

The idea is to use layers, make the textarea as top layer, the multiple lines as bottom layer.

I'm using a pseudo element for the bottom layer, since :before and :after does not work on a textarea, so I set it on the container div element.

For the bottom lines, I simply use underscores _, with \A for a line break, you can have as many lines as needed with a number of \A. The height of each line will get updated automatically according to the font size.

Jsfiddle Example

.container {
  width: 200px;
  border: 1px solid green;
  position: relative;
  overflow: hidden;
}
.container:before, .container textarea {
  font-family: sans-serif;
  font-size: 20px;
}
.container textarea {
  width: 100%;
  box-sizing: border-box;
  background-color: transparent;
  border: 0;
  outline: none;
  display: block;
  line-height: 1.2;
}
.container:before {
  position: absolute;
  content: "____________________\A____________________";
  z-index: -1;
  left: 0;
  top: 0;
  width: 100%;
  color: silver;
  line-height: 1.4;  
}

<div class="container">
  <textarea rows="3" placeholder="Hello"></textarea>
</div>