如何使用 css 制作扁平而不实心的边框？

Question

I want to make a flat border like this one,

It not should be like this one:

 .demo{ height: 60px; width: 90%; margin: 2rem auto; border-width: 5px; border-style: solid; border-color: #007bff #ddd; }

 <div class="demo"></div>

I think it was made by CSS before/ after. But Remember that It actually not made by using border property. I need the same things like this photo. I have no idea that how to made it. [Q1] Is I need many span or before after width? (Please give a simple design)

[Q2] How WordPress make their article title box? are they used before/after or many span elm? (I already inspect WordPress editor but nothing find)

Answer 1

 .demo { height: 60px; width: 90%; margin: 2rem auto; position: relative; border-left: 4px solid #000; box-sizing: border-box; }.demo::after { top: 0; left: 0; content: ''; width: 100%; height: 100%; position: absolute; box-sizing: border-box; border: 1px solid #ddd; border-left: none; }

 <div class="demo"></div>

Answer 2

Try this, its a little hack with :before property:

.demo{
    border-left: solid 5px black;
    width: 90%;
    height: 50px;
    position:relative;
}
.demo:before{
    content:"";
    top: 0;
    left: 0;
    position:absolute;
    border: 1px solid lightgray;
    border-left:none;
    width: 100%;
    height: 100%;
    box-sizing: border-box;
}

Or another way you can achieve like this:

HTML

<div class="card">
  <div class="left-pad"></div>
  <div class="demo"></div>
</div>

CSS

.card {
  display: flex;
  align-items: center;
}
.left-pad {
  width: 5px;
  height: 50px;
  background: black;
  border-top: 1px solid black;
  border-bottom: 1px solid black;
}
.demo{
    border: solid 1px gray;
    border-left: 0px;
    width: 200px;
    height: 50px;
}

May be it helps

Answer 3

Gradient can do it. Simply adjust the order to control which one will be on the top

 .demo{ height: 60px; width: 90%; margin: 2rem auto; border: 5px solid transparent; background: linear-gradient(#007bff,#007bff) left /5px 100%, /* The top layer */ linear-gradient(red,red) right /5px 100%, linear-gradient(#ddd,#ddd) bottom /100% 2px, linear-gradient(blue,blue) top /100% 2px; /* The bottom layer */ background-repeat:no-repeat; }

 <div class="demo"></div>

Answer 4

try this:- display: table;

.demo {
    display: table;
    border-collapse: collapse;
    width: 90%;
    margin: 2em auto;
}
.cell {
    display: table-cell;
    border: 1px solid #b6bdc2;
    width: 90%;
    height: 60px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    border-left-width: 4px;
    border-left-color: #5d646c;
}


<div class="demo">
  <div class="cell"></div>
</div>

May be it helps