Heap and stack data types

Heap and stack

 

• The difference in stack space allocation:

　　1. Stack: The operating system automatically allocates and releases the parameter values ​​of the stored function, the values ​​of local variables, etc. Simple data types are stored in the stack

　　2. Heap: Stores complex types (objects), which are generally allocated and released by the programmer. If the programmer does not release, they are reclaimed by the garbage collection mechanism.

 

• Storage of simple data types

The data of the value type variable is directly stored in the variable (stack space)

• Storage of complex data types

Reference type variables (stack space) are stored in the address, the real object instance is stored in the heap space

 

Common basic data types:

Number, String, Boolean, Undefined, Null, Symbol (new unique values ​​in es6 )  and  BigInt (new in es10) ;

The basic data types are accessed by value, because the actual value stored in the variable can be directly manipulated.

Reference type data:

　　Object。包含Object、Array、 function、Date、RegExp。

　　The reference data type of javascript is an object stored in the heap memory.