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arrayUnnecessaryLengthChecks

Reports unnecessary array length checks before .some() or .every() calls.

✅ This rule is included in the ts logical presets.

Array#some() returns false for an empty array, so checking array.length !== 0 or array.length > 0 before calling .some() is redundant.

Array#every() returns true for an empty array, so checking array.length === 0 before calling .every() is redundant.

This rule reports these unnecessary length checks.

Examples

Section titled “Examples”
declare const 
const array: boolean[]
array: boolean[];
const array: boolean[]
array.
Array<boolean>.length: number
Gets or sets the length of the array. This is a number one higher than the highest index in the array.
length !== 0 && 
const array: boolean[]
array.
Array<boolean>.some(predicate: (value: boolean, index: number, array: boolean[]) => unknown, thisArg?: any): boolean
Determines whether the specified callback function returns true for any element of an array.
@param ― predicate A function that accepts up to three arguments. The some method calls
the predicate function for each element in the array until the predicate returns a value
which is coercible to the Boolean value true, 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.
some(
var Boolean: BooleanConstructor
Boolean);
declare const 
const array: boolean[]
array: boolean[];
const array: boolean[]
array.
Array<boolean>.length: number
Gets or sets the length of the array. This is a number one higher than the highest index in the array.
length > 0 && 
const array: boolean[]
array.
Array<boolean>.some(predicate: (value: boolean, index: number, array: boolean[]) => unknown, thisArg?: any): boolean
Determines whether the specified callback function returns true for any element of an array.
@param ― predicate A function that accepts up to three arguments. The some method calls
the predicate function for each element in the array until the predicate returns a value
which is coercible to the Boolean value true, 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.
some(
var Boolean: BooleanConstructor
Boolean);
declare const 
const array: boolean[]
array: boolean[];
const array: boolean[]
array.
Array<boolean>.length: number
Gets or sets the length of the array. This is a number one higher than the highest index in the array.
length === 0 || 
const array: boolean[]
array.
Array<boolean>.every(predicate: (value: boolean, index: number, array: boolean[]) => 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(
var Boolean: BooleanConstructor
Boolean);

Options

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “When Not To Use It”

If you prefer explicit length checks for documentation purposes, or if your team’s coding standards require them, you may disable this rule.

Further Reading

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”
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