先来看效果图：

密文效果：

明文效果：

实现步骤

1.首先定义一个按钮标签，来显示我们的睁眼闭眼图标

<label for="password" id="for_userpassword" style="color: #fff;">密码</label>
<input class="input" type="password" name="password" id="password" value="" />
<input type="button" class="fa-eye" onclick="showhide()" id="eye"></input>

2.定义两个样式，用来展示明文、密文

/* 密码明密文样式 */
.fa-eye-slash {
	border: 0px;
	margin-bottom: -4px;
	margin-left: -35px;
	width: 24px;
	height: 20px;
	background-image: url(images/eye_open.png);
	background-repeat: no-repeat;
	background-size: 24px 24px;
	background-color: rgba(0, 0, 0, 0)
}

.fa-eye {
	border: 0px;
	margin-bottom: -4px;
	margin-left: -35px;
	width: 24px;
	height: 20px;
	background-image: url(images/eye_close.png);
	background-repeat: no-repeat;
	background-size: 24px 24px;
	background-color: rgba(0, 0, 0, 0)
}

3.定义一个方法，用来切换明密文的状态

//密码明密文显示
function showhide() {
	if (document.getElementById("password").type == "password") {
		document.getElementById("password").type = "text";
		document.getElementById("eye").className = 'fa-eye-slash'
	} else {
		document.getElementById("password").type = "password";
		document.getElementById("eye").className = 'fa-eye'
	}
}

4.到此就大功告成了