Operators.md

Operators

Abstract Equality

The == operator's behavior is defined as "The Abstract Equality Comparison Algorithm" in section 11.9.3 of the ES5 spec. The comparison x == y, where x and y are values, produces true or false.

x	y	result
undefined	undefined	true
null	null	true
null	undefined	true
NaN	any	false
+0	-0	true
object	object	are refs equal
number	string	number == toNumber(string)
bool	any	toNumber(bool) == any
string	object	string == toPrimitive(object)
number	object	number == toPrimitive(object)

Comparison in reverse order are the same any another comparison are false

Typeof

Operator that inspects the type of the given value

Example:

typeof undefined       // 'undefined'
typeof true            // 'boolean'
typeof 42              // 'number'
typeof '42'            // 'string'
typeof { life: 42 }    // 'object'
typeof null            // 'object'
typeof function a(){}  // 'function'
typeof new String("s") // 'object'
// added in ES6!
typeof Symbol()        //  'symbol'