JS Memory

jsmem.md

JavaScript Code

var str = "hi";

Memory allocation:

Address	Value	Description
......	...
0x1001	call object	Start of a call object's memory
0x1002	0x00af	Reference to invoked function
0x1003	1	Number of references in this call object
0x1004	str	Name of variable (in practice would not be in a single address)
0x1005	0x1001	Memory address of "hi"
......	...
0x2001	string	type identifier
0x2002	2	number of bytes
0x2003	h	byte of first character
0x2004	i	byte of second character

Explanation

When JS runs: var str = "hi"; by calling some function, it first hoists all variable declarations and creates a spot in memory for the variable. This might leave memory something like:

Address	Value	Description
......	...
0x1001	call object	Start of a call object's memory
0x1002	0x00af	Reference to invoked function
0x1003	1	Number of references in this call object
0x1004	str	Name of variable
0x1005	empty
......	...

In practice, the name of the variable, str, would not be held in a single memory address. Also, the variable names and locations would not be stored in a fixed-memory array (possibly in a hash-table).

Next, the string "hi" would be created in memory like:

Address	Value	Description
......	...
0x2001	string	type identifier
0x2002	2	number of bytes
0x2003	h	byte of first character
0x2004	i	byte of second character

Finally, the pointer address of str would be set to the memory address of "hi" (0x2001), leaving memory as indicated at the top of the page.