Một vài ý tưởng về hiệu ứng khi design text input field

<!DOCTYPE html>
<html lang="en" class="no-js">
	<head>
		<meta charset="UTF-8" />
		<meta http-equiv="X-UA-Compatible" content="IE=edge">
		<meta name="viewport" content="width=device-width, initial-scale=1">
		<title>Some effects</title>
		<link rel="stylesheet" type="text/css" href="normalize.css" />
		<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.css">
		<link rel="stylesheet" type="text/css" href="style.css" />
		<link rel="stylesheet" type="text/css" href="effects.css" />
		<!--[if IE]>
  		<script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
		<![endif]-->
	</head>
	<body>
		<div class="container">
		  <section class="content">
		    <a class="back" href="https://viblo.asia/euclid/posts/eBYjv45yRxpV" title="Một vài ý tưởng về hiệu ứng khi design text input field"><span>Một vài ý tưởng về hiệu ứng khi design text input field<span></a>
			</section>
			<section class="content bgcolor-1">
				<h2 class="nomargin-bottom">Top Down</h2>
				<span class="input input--top__down">
        	<input class="input__field input__field--top__down" type="text" id="input-1" />
        	<label class="input__label input__label--top__down" for="input-1">
        		<span class="input__label-content input__label-content--top__down">Name</span>
        	</label>
        </span>
			</section>
			<section class="content bgcolor-2">
				<h2>Left Right</h2>
				<span class="input input--left__right">
					<input class="input__field input__field--left__right" type="text" id="input-5" />
					<label class="input__label input__label--left__right input__label--left__right-color-2" for="input-5">
						<span class="input__label-content input__label-content--left__right">Birthday</span>
					</label>
				</span>
			</section>
			<section class="content bgcolor-3">
				<h2>Split</h2>
				<span class="input input--split">
					<input class="input__field input__field--split" type="text" id="input-7" />
					<label class="input__label input__label--split" for="input-7">
						<span class="input__label-content input__label-content--split">Phone</span>
					</label>
				</span>
			</section>
		</div><!-- /container -->
		<script src="script.js"></script>
	</body>
</html>

@import url(http://fonts.googleapis.com/css?family=Raleway:200,500,700,800);

*, *:after, *:before { -webkit-box-sizing: border-box; box-sizing: border-box; }
.clearfix:before, .clearfix:after { content: ''; display: table; }
.clearfix:after { clear: both; }

body {
	background: #f9f7f6;
	color: #404d5b;
	font-weight: 500;
	font-size: 1.05em;
	font-family: 'Raleway', Arial, sans-serif;
}

a {
	color: #2fa0ec;
	text-decoration: none;
	outline: none;
}

a:hover, a:focus {
	color: #404d5b;
}
.back {
  margin: 2em;
  font-weight: bold;
}

.container {
	margin: 0 auto;
	text-align: center;
	overflow: hidden;
}

.content {
	font-size: 150%;
	padding: 3em 0;
}

.content h2 {
	margin: 0 0 2em;
	opacity: 0.5;
}

.content p {
	margin: 1em 0;
	padding: 5em 0 0 0;
	font-size: 0.65em;
}

.bgcolor-1 { background: #f0efee; }
.bgcolor-2 { background: #f9f9f9; }
.bgcolor-3 { background: #2f3238; color: #fff; }

body .nomargin-bottom {
	margin-bottom: 0;
}

.input {
	position: relative;
	z-index: 1;
	display: inline-block;
	margin: 1em;
	max-width: 350px;
	width: calc(100% - 2em);
	vertical-align: top;
}

.input__field {
	position: relative;
	display: block;
	float: right;
	padding: 0.8em;
	width: 60%;
	border: none;
	border-radius: 0;
	background: #f0f0f0;
	color: #aaa;
	font-weight: bold;
	font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
	-webkit-appearance: none; /* for box shadows to show on iOS */
}

.input__field:focus {
	outline: none;
}

.input__label {
	display: inline-block;
	float: right;
	padding: 0 1em;
	width: 40%;
	color: #6a7989;
	font-weight: bold;
	font-size: 70.25%;
	-webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
	-webkit-touch-callout: none;
	-webkit-user-select: none;
	-khtml-user-select: none;
	-moz-user-select: none;
	-ms-user-select: none;
	user-select: none;
}

.input__label-content {
	position: relative;
	display: block;
	padding: 1.6em 0;
	width: 100%;
}

.graphic {
	position: absolute;
	top: 0;
	left: 0;
	fill: none;
}

.icon {
	color: #ddd;
	font-size: 150%;
}

article,aside,details,figcaption,figure,footer,header,hgroup,main,nav,section,summary{display:block;}audio,canvas,video{display:inline-block;}audio:not([controls]){display:none;height:0;}[hidden]{display:none;}html{font-family:sans-serif;-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%;}body{margin:0;}a:focus{outline:thin dotted;}a:active,a:hover{outline:0;}h1{font-size:2em;margin:0.67em 0;}abbr[title]{border-bottom:1px dotted;}b,strong{font-weight:bold;}dfn{font-style:italic;}hr{-moz-box-sizing:content-box;box-sizing:content-box;height:0;}mark{background:#ff0;color:#000;}code,kbd,pre,samp{font-family:monospace,serif;font-size:1em;}pre{white-space:pre-wrap;}q{quotes:"\201C" "\201D" "\2018" "\2019";}small{font-size:80%;}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline;}sup{top:-0.5em;}sub{bottom:-0.25em;}img{border:0;}svg:not(:root){overflow:hidden;}figure{margin:0;}fieldset{border:1px solid #c0c0c0;margin:0 2px;padding:0.35em 0.625em 0.75em;}legend{border:0;padding:0;}button,input,select,textarea{font-family:inherit;font-size:100%;margin:0;}button,input{line-height:normal;}button,select{text-transform:none;}button,html input[type="button"],input[type="reset"],input[type="submit"]{-webkit-appearance:button;cursor:pointer;}button[disabled],html input[disabled]{cursor:default;}input[type="checkbox"],input[type="radio"]{box-sizing:border-box;padding:0;}input[type="search"]{-webkit-appearance:textfield;-moz-box-sizing:content-box;-webkit-box-sizing:content-box;box-sizing:content-box;}input[type="search"]::-webkit-search-cancel-button,input[type="search"]::-webkit-search-decoration{-webkit-appearance:none;}button::-moz-focus-inner,input::-moz-focus-inner{border:0;padding:0;}textarea{overflow:auto;vertical-align:top;}table{border-collapse:collapse;border-spacing:0;}

/* Top Down */

.input--top__down {
	margin: 4em 1em 1em;
}

.input__field--top__down {
	padding: 0.4em 0.25em;
	width: 100%;
	background: transparent;
	color: #AFB5BB;
	font-size: 1.55em;
}

.input__label--top__down {
	position: absolute;
	width: 100%;
	text-align: left;
	pointer-events: none;
}

.input__label-content--top__down {
	-webkit-transition: -webkit-transform 0.3s;
	transition: transform 0.3s;
}

.input__label--top__down::before,
.input__label--top__down::after {
	content: '';
	position: absolute;
	left: 0;
	z-index: -1;
	width: 100%;
	height: 4px;
	background: #6a7989;
	-webkit-transition: -webkit-transform 0.3s;
	transition: transform 0.3s;
}

.input__label--top__down::before {
	top: 0;
}

.input__label--top__down::after {
	bottom: 0;
}

.input__field--top__down:focus + .input__label--top__down .input__label-content--top__down,
.input--filled .input__label-content--top__down {
	-webkit-transform: translate3d(0, -90%, 0);
	transform: translate3d(0, -90%, 0);
}

.input__field--top__down:focus + .input__label--top__down::before,
.input--filled .input__label--top__down::before {
	-webkit-transform: translate3d(0, -0.5em, 0);
	transform: translate3d(0, -0.5em, 0);
}

.input__field--top__down:focus + .input__label--top__down::after,
.input--filled .input__label--top__down::after {
	-webkit-transform: translate3d(0, 0.5em, 0);
	transform: translate3d(0, 0.5em, 0);
}


/* Left Right */

.input--left__right {
	overflow: hidden;
}

.input__field--left__right {
	margin-top: 1em;
	padding: 0.85em 0.15em;
	width: 100%;
	background: transparent;
	color: #595F6E;
}

.input__label--left__right {
	position: absolute;
	bottom: 0;
	left: 0;
	padding: 0 0.25em;
	width: 100%;
	height: calc(100% - 1em);
	text-align: left;
	pointer-events: none;
}

.input__label-content--left__right {
	position: absolute;
}

.input__label--left__right::before,
.input__label--left__right::after {
	content: '';
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: calc(100% - 10px);
	border-bottom: 1px solid #B9C1CA;
}

.input__label--left__right::after {
	margin-top: 2px;
	border-bottom: 4px solid red;
	-webkit-transform: translate3d(-100%, 0, 0);
	transform: translate3d(-100%, 0, 0);
	-webkit-transition: -webkit-transform 0.3s;
	transition: transform 0.3s;
}

.input__label--left__right-color-1::after {
	border-color: hsl(200, 100%, 50%);
}

.input__label--left__right-color-2::after {
	border-color: hsl(160, 100%, 50%);
}

.input__label--left__right-color-3::after {
	border-color: hsl(20, 100%, 50%);
}

.input__field--left__right:focus + .input__label--left__right::after,
.input--filled .input__label--left__right::after {
	-webkit-transform: translate3d(0, 0, 0);
	transform: translate3d(0, 0, 0);
}

.input__field--left__right:focus + .input__label--left__right .input__label-content--left__right,
.input--filled .input__label-content--left__right {
	-webkit-animation: anim-1 0.3s forwards;
	animation: anim-1 0.3s forwards;
}

@-webkit-keyframes anim-1 {
	50% {
		opacity: 0;
		-webkit-transform: translate3d(1em, 0, 0);
		transform: translate3d(1em, 0, 0);
	}
	51% {
		opacity: 0;
		-webkit-transform: translate3d(-1em, -40%, 0);
		transform: translate3d(-1em, -40%, 0);
	}
	100% {
		opacity: 1;
		-webkit-transform: translate3d(0, -40%, 0);
		transform: translate3d(0, -40%, 0);
	}
}

@keyframes anim-1 {
	50% {
		opacity: 0;
		-webkit-transform: translate3d(1em, 0, 0);
		transform: translate3d(1em, 0, 0);
	}
	51% {
		opacity: 0;
		-webkit-transform: translate3d(-1em, -40%, 0);
		transform: translate3d(-1em, -40%, 0);
	}
	100% {
		opacity: 1;
		-webkit-transform: translate3d(0, -40%, 0);
		transform: translate3d(0, -40%, 0);
	}
}


/* Split */

.input--split {
	max-width: 320px;
	margin-bottom: 3em;
}

.input__field--split {
	width: 100%;
	background: transparent;
	color: #9196A1;
	opacity: 0;
	text-align: center;
	-webkit-transition: opacity 0.3s;
	transition: opacity 0.3s;
}

.input__label--split {
	position: absolute;
	left: 0;
	width: 100%;
	color: #df6589;
	pointer-events: none;
}

.input__label--split::before,
.input__label--split::after {
	content: '';
	position: absolute;
	top: 0;
	left: 0;
	width: 50%;
	height: 100%;
	border: 4px solid #747981;
	-webkit-transition: -webkit-transform 0.3s;
	transition: transform 0.3s;
}

.input__label--split::before {
	border-right: none;
}

.input__label--split::after {
	left: 50%;
	border-left: none;
}

.input__field--split:focus,
.input--filled .input__field--split {
	opacity: 1;
	-webkit-transition-delay: 0.3s;
	transition-delay: 0.3s;
}

.input__field--split:focus + .input__label--split::before,
.input--filled .input__label--split::before {
	-webkit-transform: translate3d(-10%, 0, 0);
	transform: translate3d(-10%, 0, 0);
}

.input__field--split:focus + .input__label--split::after,
.input--filled .input__label--split::after {
	-webkit-transform: translate3d(10%, 0, 0);
	transform: translate3d(10%, 0, 0);
}

.input__field--split:focus + .input__label--split .input__label-content--split,
.input--filled .input__label-content--split {
	-webkit-animation: anim-2 0.3s forwards;
	animation: anim-2 0.3s forwards;
}

@-webkit-keyframes anim-2 {
	50% {
		opacity: 0;
		-webkit-transform: scale3d(0.3, 0.3, 1);
		transform: scale3d(0.3, 0.3, 1);
	}
	51% {
		opacity: 0;
		-webkit-transform: translate3d(0, 3.7em, 0) scale3d(0.3, 0.3, 1);
		transform: translate3d(0, 3.7em, 0) scale3d(0.3, 0.3, 1);
	}
	100% {
		opacity: 1;
		-webkit-transform: translate3d(0, 3.7em, 0);
		transform: translate3d(0, 3.7em, 0);
	}
}

@keyframes anim-2 {
	50% {
		opacity: 0;
		-webkit-transform: scale3d(0.3, 0.3, 1);
		transform: scale3d(0.3, 0.3, 1);
	}
	51% {
		opacity: 0;
		-webkit-transform: translate3d(0, 3.7em, 0) scale3d(0.3, 0.3, 1);
		transform: translate3d(0, 3.7em, 0) scale3d(0.3, 0.3, 1);
	}
	100% {
		opacity: 1;
		-webkit-transform: translate3d(0, 3.7em, 0);
		transform: translate3d(0, 3.7em, 0);
	}
}

/*!
 * classie - class helper functions
 * from bonzo https://github.com/ded/bonzo
 * 
 * classie.has( elem, 'my-class' ) -> true/false
 * classie.add( elem, 'my-new-class' )
 * classie.remove( elem, 'my-unwanted-class' )
 * classie.toggle( elem, 'my-class' )
 */

/*jshint browser: true, strict: true, undef: true */
/*global define: false */

( function( window ) {

'use strict';

// class helper functions from bonzo https://github.com/ded/bonzo

function classReg( className ) {
  return new RegExp("(^|\\s+)" + className + "(\\s+|$)");
}

// classList support for class management
// altho to be fair, the api sucks because it won't accept multiple classes at once
var hasClass, addClass, removeClass;

if ( 'classList' in document.documentElement ) {
  hasClass = function( elem, c ) {
    return elem.classList.contains( c );
  };
  addClass = function( elem, c ) {
    elem.classList.add( c );
  };
  removeClass = function( elem, c ) {
    elem.classList.remove( c );
  };
}
else {
  hasClass = function( elem, c ) {
    return classReg( c ).test( elem.className );
  };
  addClass = function( elem, c ) {
    if ( !hasClass( elem, c ) ) {
      elem.className = elem.className + ' ' + c;
    }
  };
  removeClass = function( elem, c ) {
    elem.className = elem.className.replace( classReg( c ), ' ' );
  };
}

function toggleClass( elem, c ) {
  var fn = hasClass( elem, c ) ? removeClass : addClass;
  fn( elem, c );
}

var classie = {
  // full names
  hasClass: hasClass,
  addClass: addClass,
  removeClass: removeClass,
  toggleClass: toggleClass,
  // short names
  has: hasClass,
  add: addClass,
  remove: removeClass,
  toggle: toggleClass
};

// transport
if ( typeof define === 'function' && define.amd ) {
  // AMD
  define( classie );
} else {
  // browser global
  window.classie = classie;
}

})( window );

(function() {
	// trim polyfill : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim
	if (!String.prototype.trim) {
		(function() {
			// Make sure we trim BOM and NBSP
			var rtrim = /^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g;
			String.prototype.trim = function() {
				return this.replace(rtrim, '');
			};
		})();
	}

	[].slice.call( document.querySelectorAll( 'input.input__field' ) ).forEach( function( inputEl ) {
		// in case the input is already filled..
		if( inputEl.value.trim() !== '' ) {
			classie.add( inputEl.parentNode, 'input--filled' );
		}

		// events:
		inputEl.addEventListener( 'focus', onInputFocus );
		inputEl.addEventListener( 'blur', onInputBlur );
	} );

	function onInputFocus( ev ) {
		classie.add( ev.target.parentNode, 'input--filled' );
	}

	function onInputBlur( ev ) {
		if( ev.target.value.trim() === '' ) {
			classie.remove( ev.target.parentNode, 'input--filled' );
		}
	}
})();