A brief analysis of the difference between 2 equal signs and 3 equal signs in js_Basic knowledge

First of all, == equality is equal, === identity is equal.

==, when the value types on both sides are different, type conversion must be performed first and then compared.

===, no type conversion is performed, and different types must not be equal.

The following are respectively explained:

Let’s talk about === first, this is relatively simple. The following rules are used to determine whether two values ​​​​are === equal:

1. If the types are different, [not equal]

2. If both are numeric values ​​and are the same value, then [equal]; (!Exception) is that if at least one of them is NaN, then [not equal]. (To determine whether a value is NaN, you can only use isNaN() to determine)

3. If both are strings and the characters at each position are the same, then [equal]; otherwise [not equal].

4. If both values ​​are true, or both are false, then [equal].

5. If both values ​​refer to the same object or function, then [equal]; otherwise [not equal].

6. If both values ​​are null, or both are undefined, then [equal].

Let’s talk about ==, according to the following rules:

1. If two value types are the same, perform === comparison.

2. If two value types are different, they may be equal. Perform type conversion and comparison according to the following rules:

a. If one is null and the other is undefined, then [equal].

b. If one is a string and the other is a numerical value, convert the string into a numerical value and then compare.

c. If any value is true