Check out example codes for "how to underline font in css". It will help you in understanding the concepts better.

Code Example 1

h1 {
  text-decoration: overline;
}

h2 {
  text-decoration: line-through;
}

h3 {
  text-decoration: underline;
}

h4 {
  text-decoration: underline overline;
}

Code Example 2

h3 {
  text-decoration: underline;
}

Learn ReactJs, React Native from akashmittal.com