JS Best ways to verify isNumber, isBoolean, isString, isObject, isArray, isInteger, isFunction

Basically,

typeof 1;
'number'

typeof 1.2;
'number'

typeof NaN;
'number'

typeof false;
'boolean'

typeof '';
'string'

typeof function () {};
'function'

typeof undefined;
'undefined'

typeof null;
'object'

typeof {};
'object'

typeof [];
'object'

Use above as reference and write isFunctions now:

isNumber

const isNumber = value => typeof value === 'number' && !isNaN(value);

isNumber(1);
true

isNumber(1.2);
true

isNumber(-1);
true

isNumber(-1.2);
true

isNumber(01);
true

isNumber(00);
true

isNumber(Infinity);
true

isNumber(-Infinity);
true

isNumber(NaN);
false

isNumber(undefined);
false

isNumber(true);
false

isNumber('23');
false

isNumber(null);
false

isNumber('');
false

isNumber('23');
false

isNumber([]);
false

isNumber({});
false

isNumber(function () {})
false

(+/-)Infinity are of type number in javascript as if you want to avoid then you can update logic as:

const isNumber = value => typeof value === 'number' && !isNaN(value) && isFinite(value);
undefined

isNumber(Infinity);
false

isNumber(-Infinity);
false

isBoolean

isBoolean = value => typeof value === 'boolean';

isBoolean(true);
true

isBoolean(false);
true

isBoolean('test');
false

isBoolean(1);
false

isBoolean(0);
false

isBoolean(undefined);
false

isBoolean(null);
false

isBoolean([]);
false

isBoolean(NaN);
false

isBoolean({});
false

isBoolean(function () {});
false

isString

const isString = value => typeof value === 'string';

isString('test');
true

isString(undefined);
false

isString(null);
false

isString(undefined);
false

isString({});
false

// you can validate remaining as they return false.

isObject

isObject = value => typeof value === 'object';

isObject({});
true

isObject([]); // failed.
true

isObject(null); // failed.
true

isObject = value => value !== null && !Array.isArray(value) && typeof value === 'object';

isObject({});
true

isObject(null);
false

isObject([]);
false

isArray

// you can directly use Array.isArray(value);

isArray = value => Array.isArray(value);

isArray([]);
true

isArray({});
false

isArray(null);
false

// Validate for other values.

isFunction

isFunction = value => typeof value === 'function';

isFunction(function() {});
true

isFunction(null);
false

isFunction(undefined);
false

isFunction({});
false

isInteger

We can use Number.isInteger(value)

Yes. There are some exceptions based on where do we use these functions.

Please do suggest if I miss any mandatory validations in above isFunctions.

Thank you!