[JS foundation] logical judgment (error prone points)

1. null instanceof Object The result is false

• null Essentially, null Type, not Object,typeof null = ‘object’ It's a legacy of history ;

2. NaN == NaN As the result of the false

• NaN It means not a number , yes Not a Number Abbreviation , But they are also different ,NaN It's not equal to NaN And NaN Can never be equal .

3. == The judgment process ：

1. To determine if there is NaN, If there is , Then return directly false;
2. To determine if there is Boolean, If there is ,false Convert to 0,true Convert to 1;
3. null、undefined No conversion ;

4. Number The value corresponding to the type conversion

Number(’ ') = 0
Number(false) = 0
Number(undefined) = NaN

5. null == undefined As the result of the true

• ECMAScript Think ： They all represent an invalid value , Indicates similar content .

6. {} === {} 、[1,2,3] === [1,2,3] As the result of the false

Address of reference type comparison , Their addresses are different .

P.S. The above explanation comes from the network , If there is something wrong with the explanation , Welcome to comment area ！