49 lines
1.2 KiB
Plaintext
49 lines
1.2 KiB
Plaintext
When either the equality operator in a test for ``++null++`` or ``++undefined++``, or the logical operator that follows it is reversed, the code has the appearance of safely null-testing the object before dereferencing it. Unfortunately the effect is just the opposite - the object is null-tested and then dereferenced only if it is ``++null++``/``++undefined++``, leading to a guaranteed ``++TypeError++``.
|
|
|
|
== Noncompliant Code Example
|
|
|
|
----
|
|
if (str == null && str.length == 0) {
|
|
console.log("String is empty");
|
|
}
|
|
|
|
if (str == undefined && str.length == 0) {
|
|
console.log("String is empty");
|
|
}
|
|
|
|
if (str != null || str.length > 0) {
|
|
console.log("String is not empty");
|
|
}
|
|
|
|
if (str != undefined || str.length > 0) {
|
|
console.log("String is not empty");
|
|
}
|
|
----
|
|
|
|
== Compliant Solution
|
|
|
|
----
|
|
if (str != null && str.length == 0) {
|
|
console.log("String is empty");
|
|
}
|
|
|
|
if (str != undefined && str.length == 0) {
|
|
console.log("String is empty");
|
|
}
|
|
|
|
if (str == null || str.length > 0) {
|
|
console.log("String is not empty");
|
|
}
|
|
|
|
if (str == undefined || str.length > 0) {
|
|
console.log("String is not empty");
|
|
}
|
|
----
|
|
|
|
ifdef::env-github,rspecator-view[]
|
|
== Comments And Links
|
|
(visible only on this page)
|
|
|
|
include::comments-and-links.adoc[]
|
|
endif::env-github,rspecator-view[]
|