is

defined

Signature

defined(value)

Description

Check if value is defined (not null or undefined)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is not null and not undefined

Examples

is.defined(0) // true
is.defined('') // true
is.defined(null) // false
is.defined(undefined) // false

nil

Signature

nil(value)

Description

Check if value is null or undefined

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is null or undefined

Examples

is.nil(null) // true
is.nil(undefined) // true
is.nil(0) // false
is.nil('') // false

plainObject

Signature

plainObject(value)

Description

Check if value is a plain object (not array, not null, not a class instance)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a plain object literal

Examples

is.plainObject({}) // true
is.plainObject({ name: 'John' }) // true
is.plainObject([]) // false
is.plainObject(null) // false
is.plainObject(new Date()) // false

emptyObject

Signature

emptyObject(value)

Description

Check if value is an empty object

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a plain object with no keys

Examples

is.emptyObject({}) // true
is.emptyObject({ name: 'John' }) // false
is.emptyObject([]) // false

string

Signature

string(value)

Description

Check if value is a string

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a string

Examples

is.string('hello') // true
is.string('') // true
is.string(123) // false

emptyString

Signature

emptyString(value)

Description

Check if value is an empty string (whitespace only)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a string with only whitespace

Examples

is.emptyString('') // true
is.emptyString('   ') // true
is.emptyString('hello') // false
is.emptyString(null) // false

number

Signature

number(value)

Description

Check if value is a valid number (not NaN, not Infinity)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a finite number

Examples

is.number(42) // true
is.number(3.14) // true
is.number(NaN) // false
is.number(Infinity) // false
is.number('42') // false

integer

Signature

integer(value)

Description

Check if value is an integer

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is an integer

Examples

is.integer(42) // true
is.integer(0) // true
is.integer(3.14) // false
is.integer('42') // false

array

Signature

array(value)

Description

Check if value is an array

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is an array

Examples

is.array([]) // true
is.array([1, 2, 3]) // true
is.array({}) // false
is.array('hello') // false

emptyArray

Signature

emptyArray(value)

Description

Check if value is an empty array

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is an array with no elements

Examples

is.emptyArray([]) // true
is.emptyArray([1, 2]) // false
is.emptyArray({}) // false

arrayOfLength

Signature

arrayOfLength(value, length)

Description

Check if value is an array of specific length

Parameters

Name	Type	Required	Description
value	*	yes	The value to check
length	number	yes	The expected length

Returns

Type	Description
boolean	True if the value is an array with the specified length

Examples

is.arrayOfLength([1, 2, 3], 3) // true
is.arrayOfLength([1, 2], 3) // false
is.arrayOfLength([], 0) // true

function

Signature

function(value)

Description

Check if value is a function

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a function

Examples

is.function(() => {}) // true
is.function(function() {}) // true
is.function(Array.isArray) // true
is.function({}) // false

boolean

Signature

boolean(value)

Description

Check if value is a boolean

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a boolean

Examples

is.boolean(true) // true
is.boolean(false) // true
is.boolean(1) // false
is.boolean('true') // false

oneOf

Signature

oneOf(value, allowedValues)

Description

Check if value is one of the allowed values

Parameters

Name	Type	Required	Description
value	*	yes	The value to check
allowedValues	Array	yes	Array of allowed values

Returns

Type	Description
boolean	True if the value is included in allowedValues

Examples

is.oneOf('red', ['red', 'green', 'blue']) // true
is.oneOf('yellow', ['red', 'green', 'blue']) // false
is.oneOf(2, [1, 2, 3]) // true

positive

Signature

positive(value)

Description

Check if value is a positive number

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a number greater than 0

Examples

is.positive(5) // true
is.positive(0.1) // true
is.positive(0) // false
is.positive(-5) // false

negative

Signature

negative(value)

Description

Check if value is a negative number

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is a number less than 0

Examples

is.negative(-5) // true
is.negative(-0.1) // true
is.negative(0) // false
is.negative(5) // false

inRange

Signature

inRange(value, min, max)

Description

Check if value is within a numeric range (inclusive)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check
min	number	yes	Minimum value (inclusive)
max	number	yes	Maximum value (inclusive)

Returns

Type	Description
boolean	True if the value is a number between min and max (inclusive)

Examples

is.inRange(5, 1, 10) // true
is.inRange(1, 1, 10) // true
is.inRange(10, 1, 10) // true
is.inRange(0, 1, 10) // false
is.inRange(11, 1, 10) // false

empty

Signature

empty(value)

Description

Check if value is empty (null, undefined, empty string, empty array, or empty object)

Parameters

Name	Type	Required	Description
value	*	yes	The value to check

Returns

Type	Description
boolean	True if the value is considered empty

Examples

is.empty(null) // true
is.empty(undefined) // true
is.empty('') // true
is.empty('   ') // true
is.empty([]) // true
is.empty({}) // true
is.empty(0) // false
is.empty(false) // false
is.empty('hello') // false