== Why is this an issue?

A chain of ``++if-else-if++`` or ``++switch-case++`` statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to ``++true++`` or that matches the discriminant of the ``++switch++``.


Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior.


 


_Note that this rule requires Node.js to be available during analysis._

=== Noncompliant code example

[source,javascript]
----
if (param == 1)
  openWindow();
else if (param == 2)
  closeWindow();
else if (param == 1)  // Noncompliant
  moveWindowToTheBackground();

switch (param) {
  case 1:
    openWindow();
    break;
  case 2:
    closeWindow();
    break;
  case 1: // Noncompliant
    moveWindowToTheBackground();
    break;
}
----

=== Compliant solution

[source,javascript]
----
if (param == 1)
  openWindow();
else if (param == 2)
  closeWindow();
else if (param == 3)
  moveWindowToTheBackground();

switch (param) {
  case 1:
    openWindow();
    break;
  case 2:
    closeWindow();
    break;
  case 3:
    moveWindowToTheBackground();
    break;
}
----


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

This branch duplicates the one on line n.


include::../highlighting.adoc[]

'''
== Comments And Links
(visible only on this page)

include::../comments-and-links.adoc[]
endif::env-github,rspecator-view[]