JavaScript - how to check if value is object?

The first important thing is what is primitive type in JavaScript?

Primitive type literals:

• 0, 1, 2, -4, NaN, +Infinity, -Infinity, etc.
• 'abc', '', etc.
• true / false
• undefined
• null -  special case, but we treat it as not defined object too

Everything else is object type!

In the below code shows how to check if value is object.

Custom method

Object function example

// ONLINE-RUNNER:browser;

function isObject(value) {
    return value === Object(value);
}


// Usage example:

console.log( isObject(null)       );  // false
console.log( isObject(undefined)  );  // false
console.log( isObject(false)      );  // false
console.log( isObject(true)       );  // false
console.log( isObject(0)          );  // false
console.log( isObject(1)          );  // false
console.log( isObject(NaN)        );  // false
console.log( isObject(+Infinity)  );  // false
console.log( isObject('')         );  // false

console.log( isObject([ ])                 );  // true
console.log( isObject({ })                 );  // true
console.log( isObject(function(){ })       );  // true
console.log( isObject(new Number(1))       );  // true
console.log( isObject(Object.prototype)    );  // true
console.log( isObject(Object.create(null)) );  // true

typeof operator example

// ONLINE-RUNNER:browser;

function isObject(value) {
    if (value == null) {  // null or undefined
        return false;
    }
  	var type = typeof value;
  	return type === 'function' || type === 'object';
}


// Usage example:

console.log( isObject(null)       );  // false
console.log( isObject(undefined)  );  // false
console.log( isObject(false)      );  // false
console.log( isObject(true)       );  // false
console.log( isObject(0)          );  // false
console.log( isObject(1)          );  // false
console.log( isObject(NaN)        );  // false
console.log( isObject(+Infinity)  );  // false
console.log( isObject('')         );  // false

console.log( isObject([ ])                 );  // true
console.log( isObject({ })                 );  // true
console.log( isObject(function(){ })       );  // true
console.log( isObject(new Number(1))       );  // true
console.log( isObject(Object.prototype)    );  // true
console.log( isObject(Object.create(null)) );  // true