Closes #1486 Add rule for no-else-return - New Javascript rule

pmd-javascript/src/main/resources/rulesets/ecmascript/unnecessary.xml

@@ -71,4 +71,37 @@ if (bar) {
     </example>
   </rule>
 
+  <rule name="NoElseReturn"
+        language="ecmascript"
+        since="5.5.0"
+        message="The else block is unnecessary"
+        class="net.sourceforge.pmd.lang.rule.XPathRule"
+        externalInfoUrl="${pmd.website.baseurl}/rules/ecmascript/unnecessary.html#NoElseReturn">
+    <description>The else block in a if-else-construct is unnecessary if the `if` block contains a return.
+    Then the content of the else block can be put outside.
+    
+    See also: http://eslint.org/docs/rules/no-else-return
+    </description>
+    <priority>3</priority>
+    <properties>
+        <property name="xpath"><value><![CDATA[
+//IfStatement[@Else="true"][Scope[1]/ReturnStatement]
+        ]]></value></property>
+    </properties>
+    <example><![CDATA[
+// Bad:
+if (x) {
+  return y;
+} else {
+  return z;
+}
+
+// Good:
+if (x) {
+  return y;
+}
+return z;
+    ]]></example>
+  </rule>
+
 </ruleset>

pmd-javascript/src/test/java/net/sourceforge/pmd/lang/ecmascript/rule/unnecessary/UnnecessaryRulesTest.java

@@ -13,5 +13,6 @@ public class UnnecessaryRulesTest extends SimpleAggregatorTst {
     public void setUp() {
         addRule(RULESET, "UnnecessaryBlock");
         addRule(RULESET, "UnnecessaryParentheses");
+        addRule(RULESET, "NoElseReturn");
     }
 }

pmd-javascript/src/test/resources/net/sourceforge/pmd/lang/ecmascript/rule/unnecessary/xml/NoElseReturn.xml

@@ -0,0 +1,45 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<test-data>
+    <test-code>
+        <description>Simple violation</description>
+        <expected-problems>1</expected-problems>
+        <code><![CDATA[
+function foo() {
+    if (x) {
+        return y;
+    } else {
+        return z;
+    }
+}
+        ]]></code>
+    </test-code>
+
+    <test-code>
+        <description>Simple fix</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+function foo() {
+    if (x) {
+        return y;
+    }
+    return z;
+}
+        ]]></code>
+    </test-code>
+
+    <test-code>
+        <description>No return in if</description>
+        <expected-problems>0</expected-problems>
+        <code><![CDATA[
+function foo() {
+    if (x) {
+        x++;
+    } else {
+        return z;
+    }
+    return x;
+}
+        ]]></code>
+    </test-code>
+
+</test-data>