On the storage of JS data type

backgroundA classic question, first thrown to the folks to see:

var a = "Black Mao"; var b = a;var C = new Object (); var d = c;a = "New Black Mao"; c.age = 24;//print out what's the result? Console.log (A, B, C, D);

Above first put the problem out, after the carding, then look back to see the process. What are the data types of JS? JS packet content large data type, one is the basic data type (String, number, Boolean, undefined, null), and the other is a reference type (Object) What is the way data is stored?

• Stack: The value of the parameter that holds the function, the values of the local variables (advanced post-exit)
• Heap area: Distributed by programmers, distributed in a similar list (in any order)
• Global zones: Global variables and static variables
• Literal constant Area: constant
• Program code area: function binary code

How are the underlying types and reference types stored in JS? The underlying type of data is stored in the stack, to give a simple example

var name = "Black Mao"; function Hello (user) {console.log (' hello ' + user);} Hello (name);//focus only on the storage of variables

Key	Value
Name	Black Mao
User	Undefined

Data for reference types are stored in the heap area, for example

var a = new Object ();//Because the heap area is similar to a list, it is simple to use the list

Key	Value
A	Object A Address

Value of Object A: object{}

...

Another: The data stored in the heap is based on the address lookup value, and does not follow the queue or the stack's entry order Review

Look back at the beginning of the article, throw that question. You can reproduce the process from creation to assignment according to the storage method described above.

var a = "Black Mao"; var b = a;var C = new Object (); var d = c;

Storage structure of the stack area:

Key	Value
A	Black Mao
B	Black Mao
C	Object C Address
D	Object C Address

Heap Area storage structure:

Value of Object C: object{}

...

...

A = "New Black Mao"; c.age = 24;

Storage structure of the stack area:

Key	Value
A	New Black Mao
B	Black Mao
C	Object C Address
D	Object C Address

Heap Area storage structure:

Value of Object C: object{age:24}

...

...

Console.log (A, B, C, d);//New Black Mao black Mao Object{age:24} object{age:24}

SummaryClarify the process to make it more efficient and error-free when writing code. Organize at any time, also prevent oneself forget ~ reference: http://blog.jobbole.com/81010/http://blog.jobbole.com/81011/http://blog.jobbole.com/81018/

On the storage of JS data type