Adding border to CSS triangle [duplicate]

问题

This question already has answers here:

CSS triangle custom border color (5 answers)

Closed 4 years ago.

I have a triangle

<div class="triangle-left"></div>


.triangle-left {
    width: 0; 
    height: 0; 
    border-top: 22px solid transparent;
    border-bottom: 22px solid transparent;
    border-right: 22px solid white;
}

How do I draw the outline of a CSS triangle, considering border itself is used to make the triangle? External divs?

回答1:

One way to do it is the create an inner triangle which is smaller.

.triangle-left {
    width: 0;
    height: 0;
    border-top: 23px solid transparent;
    border-bottom: 23px solid transparent;
    border-right: 23px solid red;
}

.inner-triangle {
    position: relative;
    top: -20px;
    left: 2px;
    width: 0;
    height: 0;
    border-top: 20px solid transparent;
    border-bottom: 20px solid transparent;
    border-right: 20px solid blue;
}

<div class="triangle-left">
    <div class="inner-triangle"></div>
</div>

回答2:

This is how I would do it.

.triangle-left {
  width: 0;
  height: 0;
  border-top: 22px solid transparent;
  border-bottom: 22px solid transparent;
  border-right: 22px solid black;
  position: relative;
}

.triangle-left:after {
  content: '';
  width: 0;
  height: 0;
  border-top: 21px solid transparent;
  border-bottom: 21px solid transparent;
  border-right: 21px solid #dddddd;
  position: absolute;
  top: -21px;
  left: 1px;
}

<div class="triangle-left"></div>

Here it is on JSFiddle.

来源：https://stackoverflow.com/questions/29001636/adding-border-to-css-triangle