Learning JavaScript Data Structures and Algorithms - Third Edition

Functions of the equals operators (== and ===)

The two equals operators supported by JavaScript can cause a little bit of confusion when working with them.

When using ==, values can be considered equal even when they are of different types. This can be confusing even for a senior JavaScript developer. Let's analyze how == works using the following table:

Type(x)	Type(y)	Result
null	undefined	true
undefined	null	true
Number	String	x == toNumber(y)
String	Number	toNumber(x) == y
Boolean	Any	toNumber(x) == y
Any	Boolean	x == toNumber(y)
String or Number	Object	x == toPrimitive(y)
Object	String or number	toPrimitive(x) == y

 

If x and y are of the same type, then JavaScript ...