noUnreachable (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v1.0.0
Diagnostic Category: lint/correctness/noUnreachable
This rule is recommended, meaning it is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is error.
Sources:
- Same as no-unreachable

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "correctness": {
5
        "noUnreachable": "error"
6
      }
7
    }
8
  }
9
}

Description

Disallow code that can never run.

Statements after return, throw, break, or continue cannot execute. Unreachable code is often left by mistake after a refactor and can hide intended behavior.

Examples

Invalid

1
function example() {
2
    return;
3
    neverCalled();
4
}

code-block.js:3:5 lint/correctness/noUnreachable ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This code will never be reached ...
  
    1 │ function example() {
    2 │     return;
  > 3 │     neverCalled();
      │     ^^^^^^^^^^^^^^
    4 │ }
    5 │ 
  
  ℹ ... because this statement will return from the function beforehand
  
    1 │ function example() {
  > 2 │     return;
      │     ^^^^^^^
    3 │     neverCalled();
    4 │ }

1
function example(condition) {
2
    while (condition) {
3
        break;
4
        neverCalled();
5
    }
6
}

code-block.js:4:9 lint/correctness/noUnreachable ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This code will never be reached ...
  
    2 │     while (condition) {
    3 │         break;
  > 4 │         neverCalled();
      │         ^^^^^^^^^^^^^^
    5 │     }
    6 │ }
  
  ℹ ... because this statement will break the flow of the code beforehand
  
    1 │ function example(condition) {
    2 │     while (condition) {
  > 3 │         break;
      │         ^^^^^^
    4 │         neverCalled();
    5 │     }

1
function example() {
2
    for (const key in value) {
3
        continue;
4
        neverCalled();
5
    }
6
}

code-block.js:4:9 lint/correctness/noUnreachable ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This code will never be reached ...
  
    2 │     for (const key in value) {
    3 │         continue;
  > 4 │         neverCalled();
      │         ^^^^^^^^^^^^^^
    5 │     }
    6 │ }
  
  ℹ ... because this statement will continue the loop beforehand
  
    1 │ function example() {
    2 │     for (const key in value) {
  > 3 │         continue;
      │         ^^^^^^^^^
    4 │         neverCalled();
    5 │     }

Valid

1
function example(condition) {
2
    if (condition) {
3
        return;
4
    }
5
    alwaysCalled();
6
}