Deep understanding of JavaScript null and undefined

There are two easy-to-ignore questions in JavaScript, null==undefined and null!==undefined.

The syntax in javascript specifies that = = is the judgment value equal, = = = is the judgment value and type are equal.

This needs to be distinguished, undefined represents a basic data type that does not have an assignment, and null represents a reference data type that has no assignment.

Null is the process reference, it is in the heap, and undefined is the original value, it is in the stack.

Null means there is no object, meaning there should be no value at all,

Undefined indicates that a value is missing, that is, there should be a value here, but there is no definition.

One thing to emphasize here is that NULL participates in the data operation when its value is automatically converted to 0, and the result must be Nan when undefined participates.

Deep understanding of JavaScript null and undefined