Editing Closure (computer programming) (section)

=== Lexical environment ===
As different languages do not always have a common definition of the lexical environment, their definitions of closure may vary also. The commonly held minimalist definition of the lexical environment defines it as a set of all [[Name binding|bindings of variables]] in the scope, and that is also what closures in any language have to capture. However the meaning of a [[Variable (programming)|variable]] binding also differs. In imperative languages, variables bind to relative locations in memory that can store values.  Although the relative location of a binding does not change at runtime, the value in the bound location can. In such languages, since closure captures the binding, any operation on the variable, whether done from the closure or not, are performed on the same relative memory location. This is often called capturing the variable "by reference". Here is an example illustrating the concept in [[ECMAScript]], which is one such language:

<syntaxhighlight lang="javascript">
// Javascript
var f, g;
function foo() {
  var x;
  f = function() { return ++x; };
  g = function() { return --x; };
  x = 1;
  alert('inside foo, call to f(): ' + f());
}
foo();  // 2
alert('call to g(): ' + g());  // 1 (--x)
alert('call to g(): ' + g());  // 0 (--x)
alert('call to f(): ' + f());  // 1 (++x)
alert('call to f(): ' + f());  // 2 (++x)
</syntaxhighlight>

Function <code>foo</code> and the closures referred to by variables <code>f</code> and <code>g</code> all use the same relative memory location signified by local variable <code>x</code>.

In some instances the above behaviour may be undesirable, and it is necessary to bind a different lexical closure. Again in ECMAScript, this would be done using the <code>Function.bind()</code>.