Comparison rules for different types of javascript objects

Type (x)	Type (y)	Result
Type (x) = type (y)		X = y
Otherwise...		False
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

 

Example 1:

[0] = true;

First, the toNumber of ture will be implemented, and the result is 1. The formula is as follows and the conversion is [0] = 1.

Then [0] will be toString (), the result is "0", and the formula is converted to "0" = 1

Then "0" will be toNumber (), the result is 0, and the formula is converted to 0 = 1

Finally, according to type (x) = type (y), the formula is converted to 0 = 1

Therefore, if [0] = true, false is returned.

 

Example 2:

"Potato" = true;

First, "true" is converted to "potato" = 1, and the result is 1.

Then "potato" will be toNumber and the result will be NaN. The formula is converted to NaN = 1.

According to typeof (x) = typeof (y), the formula is converted to NaN = 1

So "potato" = true will get false

 

Example 3:

Object with getValue

Str = new Number (1 );

Str. toString = function () {return "2 "};

Str = 1;

 

Here, typeof str = "object", so toPrimitive is applied to str. Here, valueOf is used to obtain 1.

So the formula is converted to 1 = 1

So str = 1 to get true

 

Example 4:

Object with toString

Var obj = {

ToString: function () {return "2 "}

};

Obj = 1

 

Here typeof obj = "object", toPrimitive for obj, first valueOf to get the object, continue toString () to get "2", formula for "2" = 1

Perform the toNumber operation on "2" to get 2, and convert the formula to 2 = 1.

So obj = 1 to get false.

 

 

Example 5:

[] = []

The left and right are different objects, so false

! [] = []

First! [] = False, here [] is an existing object. If you force it to be of the bool type, pass !! [] To get true, so! [] = False. The formula is set to false = []

Then false is set to 0, and the formula is set to 0 = [].

Then [] for "", the formula is for "0 =""

Then, convert "" to 0, and the formula is set to 0 = 0.

So! [] = [] To get true

Example 6:

! {}= {}

First! {} Is designed for "false". The rule is the same as "5", and the formula is converted to "false == {}

False is set to 0, and the formula is converted to 0 == {}

Perform toPrimitive on {} to get "[object Object]". The formula is designed for 0 = "[object Object]".

Perform toNumber on "[object Object]" to get NaN. The formula is set to 0 = NaN.

So! {}={} Returns false.