用CSS绘制三角形箭头

CSS代码:

/* create an arrow that points up */
div.arrow-up {
    width: 0;
    height: 0;
    border-left: 5px solid transparent;  /* left arrow slant */
    border-right: 5px solid transparent; /* right arrow slant */
    border-bottom: 5px solid #2f2f2f; /* bottom, add background color here */
    font-size: 0;
    line-height: 0;
}
 
/* create an arrow that points down */
div.arrow-down {
    width: 0;
    height: 0;
    border-left: 5px solid transparent;
    border-right: 5px solid transparent;
    border-top: 5px solid #2f2f2f;
    font-size: 0;
    line-height: 0;
}
 
/* create an arrow that points left */
div.arrow-left {
    width: 0;
    height: 0;
    border-bottom: 5px solid transparent;  /* left arrow slant */
    border-top: 5px solid transparent; /* right arrow slant */
    border-right: 5px solid #2f2f2f; /* bottom, add background color here */
    font-size: 0;
    line-height: 0;
}
 
/* create an arrow that points right */
div.arrow-right {
    width: 0;
    height: 0;
    border-bottom: 5px solid transparent;  /* left arrow slant */
    border-top: 5px solid transparent; /* right arrow slant */
    border-left: 5px solid #2f2f2f; /* bottom, add background color here */
    font-size: 0;
    line-height: 0;
}

绘制这些三角形的关键在于，你要让箭头所指方向的两个侧边有很粗的边框。而背向箭头方向的一边也是同样粗的边框，而这条边的颜色就是你的三角形的颜色。边框越粗，三角形越大。用这种方法你可以绘制出各种颜色、各种大小、各种朝向的箭头。最妙的是，你只需要几行CSS代码就能实现这种效果。