rspec/rules/S2703/javascript/rule.adoc

== Why is this an issue?

JavaScript variable scope can be particularly difficult to understand and get right. The situation gets even worse when you consider the _accidental_ creation of global variables, which is what happens when you declare a variable inside a function or the ``++for++`` clause of a for-loop without using the ``++let++``, ``++const++`` or ``++var++`` keywords. 


``++let++`` and ``++const++`` were introduced in ECMAScript 2015, and are now the preferred keywords for variable declaration.


=== Noncompliant code example

[source,javascript]
----
function f(){
  i = 1;         // Noncompliant; i is global

  for (j = 0; j < array.length; j++) {  // Noncompliant; j is global now too
    // ...
  }
}
----


=== Compliant solution

[source,javascript]
----
function f(){
  var i = 1;

  for (let j = 0; j < array.length; j++) { 
    // ...
  }
}
----


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

'''
== Implementation Specification
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=== Message

Add the "let", "const" or "var" keyword to this declaration of "{0}" to make it explicit.


'''
== Comments And Links
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=== is related to: S3798

=== on 13 Mar 2015, 13:49:55 Ann Campbell wrote:
I modified the code sample you provided, [~linda.martin]. Feel free to change it back.

=== on 13 Mar 2015, 14:02:49 Linda Martin wrote:
\[~ann.campbell.2] From the description it seems that each type you declare a variable without the keyword "var" it creates a global variable. Whereas it is only within for-loops and functions that that it creates a global variable.

Maybe it's my understanding of english that it's questionable or I wrongly expressed myself when I first described the rule ?

=== on 19 May 2015, 14:09:17 Linda Martin wrote:
Reviewed.

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