first question:
There are six types of raw js, before there are five, now more Symbol ,
1. number (integer, float int / float)
2. string string
3.bollean Boolean (true false)
4.null (null)
5.undefined (null, no, do not exist)
6.symbol
Extend it, the difference between null and undefined?
null denotes a null object pointer, a variable is assigned to be an object, but has no value at this time may be assigned null
1 var a = null
2 console.log(a) // null
undefined variables have been declared, but not initialized, (indicating that the variable is defined, but no assignment)
1 var b; 2 console.log(b) // undefined
second question:
1. The basic data types of storage
In the form stored in stack, with the assignment to the data itself is stored, a type of determines the type of storage space is fixed.
1 var c = 4 2 console.log(c) // 4 3 var c = 5 4 console.log(c) // 5
2. The reference type Object
In heap stored, stored in the assignment of a pointer to an object, with the instance of the type is determined, the storage space is not fixed
var d = {} d.a = '123' d.b = '234' console.log(d) // {a: '123', b: '234'}
The third question: null is object?
Express my own point of view, null is not an object, he was just an empty object pointer, null instance of object ===> false