arrayCallbackReturns

Reports missing return statements in callbacks of array methods.

✅ This rule is included in the ts untyped presets.

Array methods like map, filter, find, some, every, and reduce rely on return values from their callbacks to function correctly. Forgetting to include a return statement in these callbacks is a common mistake that can lead to unexpected results.

If you don’t need the return value, consider using forEach instead.

const 
const result: void[]
result = 
const values: number[]
values.
Array<number>.map<void>(callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any): void[]
Calls a defined callback function on each element of an array, and returns an array that contains the results.
@param ― callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
map((
value: number
value) => {
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@see ― source
console.
Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
@since ― v0.1.100
log(
value: number
value);
});

const 
const found: number | undefined
found = 
const values: number[]
values.
Array<number>.find(predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number | undefined (+1 overload)
Returns the value of the first element in the array where predicate is true, and undefined
otherwise.
@param ― predicate find calls predicate once for each element of the array, in ascending
order, until it finds one where predicate returns true. If such an element is found, find
immediately returns that element value. Otherwise, find returns undefined.
@param ― thisArg If provided, it will be used as the this value for each invocation of
predicate. If it is not provided, undefined is used instead.
find((
value: number
value) => {
  
value: number
value === 
const target: number
target;
});

const 
const total: number
total = 
const values: number[]
values.
Array<number>.reduce(callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number (+2 overloads)
Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
@param ― callbackfn A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
@param ― initialValue If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
reduce((
sum: number
sum, 
value: number
value) => {
  
sum: number
sum + 
value: number
value;
}, 0);

const 
const valid: boolean
valid = 
const values: number[]
values.
Array<number>.every(predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean (+1 overload)
Determines whether all the members of an array satisfy the specified test.
@param ― predicate A function that accepts up to three arguments. The every method calls
the predicate function for each element in the array until the predicate returns a value
which is coercible to the Boolean value false, or until the end of the array.
@param ― thisArg An object to which the this keyword can refer in the predicate function.
If thisArg is omitted, undefined is used as the this value.
every((
value: number
value) => {
  
value: number
value > 0;
});

const 
const result: number[]
result = 
const values: number[]
values.
Array<number>.map<number>(callbackfn: (value: number, index: number, array: number[]) => number, thisArg?: any): number[]
Calls a defined callback function on each element of an array, and returns an array that contains the results.
@param ― callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
map((
value: number
value) => {
  return 
value: number
value * 2;
});

const 
const result: number[]
result = 
const values: number[]
values.
Array<number>.map<number>(callbackfn: (value: number, index: number, array: number[]) => number, thisArg?: any): number[]
Calls a defined callback function on each element of an array, and returns an array that contains the results.
@param ― callbackfn A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
map((
value: number
value) => 
value: number
value * 2);

const 
const found: number | undefined
found = 
const values: number[]
values.
Array<number>.find(predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number | undefined (+1 overload)
Returns the value of the first element in the array where predicate is true, and undefined
otherwise.
@param ― predicate find calls predicate once for each element of the array, in ascending
order, until it finds one where predicate returns true. If such an element is found, find
immediately returns that element value. Otherwise, find returns undefined.
@param ― thisArg If provided, it will be used as the this value for each invocation of
predicate. If it is not provided, undefined is used instead.
find((
value: number
value) => {
  return 
value: number
value === 
const target: number
target;
});

const 
const total: number
total = 
const values: number[]
values.
Array<number>.reduce(callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number (+2 overloads)
Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
@param ― callbackfn A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
@param ― initialValue If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
reduce((
sum: number
sum, 
value: number
value) => {
  return 
sum: number
sum + 
value: number
value;
}, 0);


const values: number[]
values.
Array<number>.forEach(callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any): void
Performs the specified action for each element in an array.
@param ― callbackfn A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
@param ― thisArg An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
forEach((
value: number
value) => {
  
var console: Console
The console module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:

A Console class with methods such as console.log(), console.error() and console.warn() that can be used to write to any Node.js stream.
A global console instance configured to write to process.stdout and
process.stderr. The global console can be used without importing the node:console module.

Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O for
more information.
Example using the global console:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
//   Error: Whoops, something bad happened
//     at [eval]:5:15
//     at Script.runInThisContext (node:vm:132:18)
//     at Object.runInThisContext (node:vm:309:38)
//     at node:internal/process/execution:77:19
//     at [eval]-wrapper:6:22
//     at evalScript (node:internal/process/execution:76:60)
//     at node:internal/main/eval_string:23:3

const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);

myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err

const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@see ― source
console.
Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format() for more information.
@since ― v0.1.100
log(
value: number
value);
});

Options

This rule is not configurable.

When Not To Use It

If you intentionally use array methods without return values in callbacks (relying on side effects), you may want to disable this rule. However, using forEach for side-effect-only iterations is more idiomatic.

Equivalents in Other Linters

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arrayCallbackReturns

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters