Reading a non-existent property on a non-undefined and non-null value will return undefined.

Noncompliant Code Example

x = 42;
y = x.length;   // Noncompliant, Number type doesn't have "length" property

Exceptions

The Ember framework introduces a few extensions to a String built-in. Since it is a widely used package, the following String properties will not trigger this rule even though they are not built-in: