rspec/rules/S1854/javascript/rule.adoc

include::../why.adoc[]

=== Exceptions

The rule ignores

 * Initializations to `-1`, `0`, `1`, `undefined`, `[]`, `{}`, `true`, `false` and `""`.
 * Variables that start with an underscore (e.g. ``++_unused++``) are ignored.
 * Assignment of `null` is ignored because it is sometimes used to help garbage collection
 * Increment and decrement expressions are ignored because they are often used idiomatically instead of `x+1`
 * This rule also ignores variables declared with object destructuring using rest syntax (used to exclude some properties from object)

[source,javascript]
----
let {a, b, ...rest} = obj;  // 'a' and 'b' are compliant
doSomething(rest);

let [x1, x2, x3] = arr;     // 'x1' is noncompliant, as omitting syntax can be used: "let [, x2, x3] = arr;"
doSomething(x2, x3);
----

include::../howtofixit.adoc[]

=== Code examples

==== Noncompliant code example

[source,javascript,diff-id=1,diff-type=noncompliant]
----
function foo(y) {
  let x = 100; // Noncompliant: dead store
  x = 150;     // Noncompliant: dead store
  x = 200;
  return x + y;
}
----

==== Compliant solution

[source,javascript,diff-id=1,diff-type=compliant]
----
function foo(y) {
  let x = 200; // Compliant: no unnecessary assignment
  return x + y;
}
----

include::../see.adoc[]

=== Related rules

* S1763 - All code should be reachable
* S2589 - Boolean expressions should not be gratuitous
* S3516 - Function returns should not be invariant
* S3626 - Jump statements should not be redundant

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

include::../message.adoc[]

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]