Learn JavaScript first chapter variables from mind map

1. When the variable is a value type, it is stored in the stack, and the value itself is saved and copied, and the variables stored in the stack are fixed in memory.

2. The reference type is stored in the heap, and a pointer to the object is saved and copied, using the new () method to construct the object when the reference type

3. Global variable: A variable without var defined outside the function or defined inside a function can be called at any location, unless it is displayed and is always present

4. Precedence of variables, local variables > Parametric variables > Global variables

Learn JavaScript first chapter variables from mind map