使用JavaScript进行即时验证 - 不确定从何处开始

//PENDING

body {
  font-family: "Raleway", sans-serif;
  font-size: 14pt;
  /* 1em */
  color: white;
  text-align: center;
  background-image: url(./img/bg);
}
#cog {
  margin-top: 5%;
  margin-bottom: -5%;
}
section.hero {
  padding: none;
  margin-left: 10%;
  margin-right: 10%;
}
section.hero h1.heroText {
  font-size: 3em;
  font-weight: 100;
}
section.hero h1.subText {
  font-size: 1.5em;
  font-weight: 100;
}
div.footer {
  font-size: 1.75em;
  font-weight: 100;
  position: absolute;
  bottom: 5px;
  width: 100%;
  text-align: center;
}
input.nicerInput {
  height: 50px;
  width: 25%;
  outline: none;
  background-color: white;
  color: #aaa;
  font-size: 1em;
  text-align: center;
  font-family: "Raleway", sans-serif;
  font-weight: 100;
  display: inline-block;
}
input.submitButton {
  color: white;
  font-family: "Raleway", sans-serif;
  font-weight: 100;
  font-size: 1em;
  height: 56px;
  width: 150px;
  background-color: #5CCF58;
  text-decoration: none;
  text-align: center;
  outline: none;
  border: none;
  display: inline-block;
  position: relative;
  left: -6px;
  top: -1px;
  -webkit-transition: linear all 1s;
  -moz-transition: linear all 1s;
  -mos-transition: linear all 1s;
}
input.submitButton:hover {
  color: inherit;
  background-color: #28CD20;
  -webkit-transition: linear all 0.5s;
  -moz-transition: linear all 0.5s;
  -mos-transition: linear all 0.5s;
}
input.submitButton:active {
  color: inherit;
  background-color: #21B71C;
  -webkit-transition: linear all 0.1s;
  -moz-transition: linear all 0.1s;
  -mos-transition: linear all 0.1s;
}
.errorMsg {
  color: white;
  font-size: 1em;
  margin-left: 10%;
  margin-right: 10%;
  display: none;
}
.fa-spin-custom {
  -webkit-animation: spin 7500ms infinite linear;
  animation: spin 7500ms infinite linear;
}
@-webkit-keyframes spin {
  0% {
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(359deg);
    transform: rotate(359deg);
  }
}
@keyframes spin {
  0% {
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(359deg);
    transform: rotate(359deg);
  }
}
.fa-7x {
  font-size: 7.5em !important;
}body {
  font-family: