CSS: Skip falsy values in `addClass( array )`, compress code

This change makes jQuery skip falsy values in `addClass( array )`
& `removeClass( array )` instead of stopping iteration when the first falsy
value is detected. This makes code like:
```js
elem.addClass( [ "a", "", "b" ] );
```
add both the `a` & `b` classes.

The code was also optimized for size a bit so it doesn't increase the
minified gzipped size.

Fixes gh-4998
Closes gh-5003

1 files changed, 44 insertions, 40 deletions

diff --git a/src/attributes/classes.js b/src/attributes/classes.js
index 796fbcc80..5e64ea2ae 100644
--- a/src/attributes/classes.js
+++ b/src/attributes/classes.js
@@ -20,8 +20,7 @@ function classesToArray( value ) {
 
 jQuery.fn.extend( {
 	addClass: function( value ) {
-		var classes, elem, cur, curValue, clazz, j, finalValue,
-			i = 0;
+		var classNames, cur, curValue, className, i, finalValue;
 
 		if ( typeof value === "function" ) {
 			return this.each( function( j ) {
@@ -29,36 +28,35 @@ jQuery.fn.extend( {
 			} );
 		}
 
-		classes = classesToArray( value );
+		classNames = classesToArray( value );
 
-		if ( classes.length ) {
-			while ( ( elem = this[ i++ ] ) ) {
-				curValue = getClass( elem );
-				cur = elem.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
+		if ( classNames.length ) {
+			return this.each( function() {
+				curValue = getClass( this );
+				cur = this.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
 
 				if ( cur ) {
-					j = 0;
-					while ( ( clazz = classes[ j++ ] ) ) {
-						if ( cur.indexOf( " " + clazz + " " ) < 0 ) {
-							cur += clazz + " ";
+					for ( i = 0; i < classNames.length; i++ ) {
+						className = classNames[ i ];
+						if ( cur.indexOf( " " + className + " " ) < 0 ) {
+							cur += className + " ";
 						}
 					}
 
 					// Only assign if different to avoid unneeded rendering.
 					finalValue = stripAndCollapse( cur );
 					if ( curValue !== finalValue ) {
-						elem.setAttribute( "class", finalValue );
+						this.setAttribute( "class", finalValue );
 					}
 				}
-			}
+			} );
 		}
 
 		return this;
 	},
 
 	removeClass: function( value ) {
-		var classes, elem, cur, curValue, clazz, j, finalValue,
-			i = 0;
+		var classNames, cur, curValue, className, i, finalValue;
 
 		if ( typeof value === "function" ) {
 			return this.each( function( j ) {
@@ -70,38 +68,40 @@ jQuery.fn.extend( {
 			return this.attr( "class", "" );
 		}
 
-		classes = classesToArray( value );
+		classNames = classesToArray( value );
 
-		if ( classes.length ) {
-			while ( ( elem = this[ i++ ] ) ) {
-				curValue = getClass( elem );
+		if ( classNames.length ) {
+			return this.each( function() {
+				curValue = getClass( this );
 
 				// This expression is here for better compressibility (see addClass)
-				cur = elem.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
+				cur = this.nodeType === 1 && ( " " + stripAndCollapse( curValue ) + " " );
 
 				if ( cur ) {
-					j = 0;
-					while ( ( clazz = classes[ j++ ] ) ) {
+					for ( i = 0; i < classNames.length; i++ ) {
+						className = classNames[ i ];
 
 						// Remove *all* instances
-						while ( cur.indexOf( " " + clazz + " " ) > -1 ) {
-							cur = cur.replace( " " + clazz + " ", " " );
+						while ( cur.indexOf( " " + className + " " ) > -1 ) {
+							cur = cur.replace( " " + className + " ", " " );
 						}
 					}
 
 					// Only assign if different to avoid unneeded rendering.
 					finalValue = stripAndCollapse( cur );
 					if ( curValue !== finalValue ) {
-						elem.setAttribute( "class", finalValue );
+						this.setAttribute( "class", finalValue );
 					}
 				}
-			}
+			} );
 		}
 
 		return this;
 	},
 
 	toggleClass: function( value, stateVal ) {
+		var classNames, className, i, self;
+
 		if ( typeof value === "function" ) {
 			return this.each( function( i ) {
 				jQuery( this ).toggleClass(
@@ -115,24 +115,28 @@ jQuery.fn.extend( {
 			return stateVal ? this.addClass( value ) : this.removeClass( value );
 		}
 
-		return this.each( function() {
-			var className, i, self, classNames;
+		classNames = classesToArray( value );
 
-			// Toggle individual class names
-			i = 0;
-			self = jQuery( this );
-			classNames = classesToArray( value );
+		if ( classNames.length ) {
+			return this.each( function() {
 
-			while ( ( className = classNames[ i++ ] ) ) {
+				// Toggle individual class names
+				self = jQuery( this );
 
-				// Check each className given, space separated list
-				if ( self.hasClass( className ) ) {
-					self.removeClass( className );
-				} else {
-					self.addClass( className );
+				for ( i = 0; i < classNames.length; i++ ) {
+					className = classNames[ i ];
+
+					// Check each className given, space separated list
+					if ( self.hasClass( className ) ) {
+						self.removeClass( className );
+					} else {
+						self.addClass( className );
+					}
 				}
-			}
-		} );
+			} );
+		}
+
+		return this;
 	},
 
 	hasClass: function( selector ) {