c24d13b88a
Co-authored-by: Marco Borgeaud <89914223+marco-antognini-sonarsource@users.noreply.github.com>
83 lines
2.5 KiB
Plaintext
83 lines
2.5 KiB
Plaintext
== Why is this an issue?
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Nested code blocks can be used to create a new scope: variables declared within that block cannot be accessed from the outside,
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and their lifetime end at the end of the block. However, this only happens when you use ES6 `let` or `const` keywords,
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a class declaration or a function declaration (in strict mode). Otherwise, the nested block is redundant and should be removed.
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=== Exceptions
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The rule does not apply to the following cases:
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* Block statements containing variable declarations using `let` or `const` keywords or class declarations are not redundant as they create a new scope.
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[source,javascript]
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----
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{
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let x = 1;
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}
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----
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* The same applies to function declarations in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode[strict mode]
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[source,javascript]
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----
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"use strict";
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{
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function foo() {}
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}
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----
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* The rule also does not apply to the blocks that are part of the https://developer.mozilla.org/en-US/docs/Glossary/Control_flow[control flow].
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[source,javascript]
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----
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if (condition) {
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doSomething();
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}
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----
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== How to fix it
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The nested code blocks should be extracted into separate methods.
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=== Code examples
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==== Noncompliant code example
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[source,javascript,diff-id=1,diff-type=noncompliant]
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----
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{ // Noncompliant: redundant code block
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var foo = bar();
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}
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if (condition) {
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doSomething();
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{ // Noncompliant: redundant code block
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doOtherStuff();
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}
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}
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----
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==== Compliant solution
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[source,javascript,diff-id=1,diff-type=compliant]
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----
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var foo = bar();
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if (condition) {
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doSomething();
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doOtherStuff();
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}
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----
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== Resources
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=== Documentation
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* Wikipedia - https://en.wikipedia.org/wiki/Single-responsibility_principle[Single Responsibility Principle]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/block[block statement]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var[var]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let[let]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const[const]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/class[class declaration]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function[function declaration]
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* MDN web docs - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode[strict mode] |