The equality operator operates as follows:
1. If two values are of the same type, compare ===.
(ps: = = [], [] {} = = {} type is the same, compare the = = =, where the address is different, so return false)
2. If two values have different types, they may be equal.
Use the following rules to cast and compare:
(1) If null and undefined, then [equal].
(2) If either value is a string and the other value is a number, convert the string to a number before comparing equality; Call the Number() function.
(3) If any value is a Boolean, convert it to a value before comparing the equality, that is, call the Number() function.
(4) If one is an object and the other is a number or string, convert the object to a value of the underlying type and compare. The object is converted to the base type using its toString or valueOf methods. The js core built-in class will try valueOf before toString; But Date uses the toString conversion.
(ps: [] ==! []! Better than converting = = so [] = = false – > [] = = 0 – > ‘= = 0 so returns true)
(ps: {} ==! {} – > {} = = false – > {} = = 0 – > [object object] = = 0 so return false)
Supplement:
| object | The return value |
|---|---|
| Array | Returns the array object itself. |
| Boolean | Boolean value. |
| Date | The stored time is millisecond UTC from midnight on January 1, 1970. |
| Function | The function itself. |
| Number | A numeric value. |
| Object | The object itself. This is the default. |
| String | String value. |
| Math and Error objects do not have valueOf methods. |