rspec/rules/S2259/javascript/rule.adoc

When a variable is assigned an `+undefined+` or `+null+` value, it has no properties. Trying to access properties of such a variable anyway results in a `+TypeError+`, causing abrupt termination of the script if the error is not caught in a `+catch+` block. But instead of `+catch+`-ing this condition, it is best to avoid it altogether.

== Noncompliant Code Example

----
if (x === undefined) {
  console.log(x.length); // Noncompliant; TypeError will be thrown
}
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include::../see.adoc[]