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

----
function f(){
  i = 1;         // Noncompliant; i is global

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


== Compliant Solution

----
function f(){
  var i = 1;

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


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== Comments And Links
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