Feature: Implemented Selection#is() and DocumentSelection#is() methods.

src/model/documentselection.js

@@ -359,6 +359,24 @@ export default class DocumentSelection {
 		return this._selection.hasAttribute( key );
 	}
 
+	/**
+	 * Checks whether object is of given type following the convention set by
+	 * {@link module:engine/model/node~Node#is}.
+	 *
+	 *		const selection = new DocumentSelection( ... );
+	 *
+	 *		selection.is( 'selection' ); // true
+	 *		selection.is( 'documentSelection' ); // true
+	 *		selection.is( 'node' ); // false
+	 *		selection.is( 'element' ); // false
+	 *
+	 * @param {String} type
+	 * @returns {Boolean}
+	 */
+	is( type ) {
+		return type == 'selection' || type == 'documentSelection';
+	}
+
 	/**
 	 * Moves {@link module:engine/model/documentselection~DocumentSelection#focus} to the specified location.
 	 * Should be used only within the {@link module:engine/model/writer~Writer#setSelectionFocus} method.

src/model/selection.js

@@ -608,6 +608,23 @@ export default class Selection {
 		return ( nodeAfterStart instanceof Element && nodeAfterStart == nodeBeforeEnd ) ? nodeAfterStart : null;
 	}
 
+	/**
+	 * Checks whether object is of given type following the convention set by
+	 * {@link module:engine/model/node~Node#is}.
+	 *
+	 *		const selection = new Selection( ... );
+	 *
+	 *		selection.is( 'selection' ); // true
+	 *		selection.is( 'node' ); // false
+	 *		selection.is( 'element' ); // false
+	 *
+	 * @param {String} type
+	 * @returns {Boolean}
+	 */
+	is( type ) {
+		return type == 'selection';
+	}
+
 	/**
 	 * Gets elements of type "block" touched by the selection.
 	 *

tests/model/documentselection.js

@@ -490,6 +490,24 @@ describe( 'DocumentSelection', () => {
 		} );
 	} );
 
+	describe( 'is', () => {
+		it( 'should return true for selection', () => {
+			expect( selection.is( 'selection' ) ).to.be.true;
+		} );
+
+		it( 'should return true for documentSelection', () => {
+			expect( selection.is( 'documentSelection' ) ).to.be.true;
+		} );
+
+		it( 'should return false for other values', () => {
+			expect( selection.is( 'node' ) ).to.be.false;
+			expect( selection.is( 'text' ) ).to.be.false;
+			expect( selection.is( 'textProxy' ) ).to.be.false;
+			expect( selection.is( 'element' ) ).to.be.false;
+			expect( selection.is( 'rootElement' ) ).to.be.false;
+		} );
+	} );
+
 	describe( '_setTo() - set collapsed at', () => {
 		it( 'detaches all existing ranges', () => {
 			selection._setTo( [ range, liveRange ] );

tests/model/selection.js

@@ -806,6 +806,21 @@ describe( 'Selection', () => {
 		} );
 	} );
 
+	describe( 'is', () => {
+		it( 'should return true for selection', () => {
+			expect( selection.is( 'selection' ) ).to.be.true;
+		} );
+
+		it( 'should return false for other values', () => {
+			expect( selection.is( 'documentSelection' ) ).to.be.false;
+			expect( selection.is( 'node' ) ).to.be.false;
+			expect( selection.is( 'text' ) ).to.be.false;
+			expect( selection.is( 'textProxy' ) ).to.be.false;
+			expect( selection.is( 'element' ) ).to.be.false;
+			expect( selection.is( 'rootElement' ) ).to.be.false;
+		} );
+	} );
+
 	describe( 'setTo - used to collapse at start', () => {
 		it( 'should collapse to start position and fire change event', () => {
 			selection.setTo( [ range2, range1, range3 ] );