explicit-length-check.md

Enforce explicitly comparing the length property of a value

Enforce explicitly checking the length of a value array in an if condition, rather than checking the truthiness of the length, and enforce comparison style.

This rule is partly fixable.

Fail

if (string.length) {}
if (array.length) {}
if (!array.length) {}
if (array.length !== 0) {}

Pass

if (string.length > 0) {}
if (array.length > 0) {}
if (array.length === 0) {}

Zero comparisons

Enforce comparison with === 0 when checking for zero length.

Fail

if (string.length < 1) {}

Pass

if (array.length === 0) {}

Non-zero comparisons

You can define your preferred way of checking non-zero length by providing a non-zero option (greater-than by default):

{
	'unicorn/explicit-length-check': ['error', {
		'non-zero': 'not-equal'
	}]
}

The non-zero option can be configured with one of the following:

• greater-than (default)
  • Enforces non-zero to be checked with: array.length > 0
• not-equal
  • Enforces non-zero to be checked with: array.length !== 0
• greater-than-or-equal
  • Enforces non-zero to be checked with: array.length >= 1