What is js stack

Stack concept

There is no stack concept in Js. It is introduced for easier understanding and better learning:

Data type

Basic type data is called value type, and complex type is also called reference type

a. Value type, simple data type, when stored, What is stored in a variable is the value itself, so it is called a value type.

b. Reference type, complex data type. When storing, the variable stores only the address and uses it for reference, so it is called a reference data type.

Stack heap space allocation concept

1. The stack

is automatically allocated and released by the operating system to store the parameter values ​​of the function , the value of local variables, etc., the operation method is similar to the stack in the data structure.

2. Heap

stores complex types (objects), which are generally allocated and released by programmers, and can also be recycled by the garbage collection mechanism. The allocation method is similar to a linked list.

varx =5;
vary =6;
f1(x,y);
functionf1(a,b)
 {
a=a+1;
b=b+1;
console.log("a="+a);//a=6;
console.log("b="+b);//b=7;
}

Step 1: Pre-parsing process stage, all variables and functions declared by var Mention the top:

var x，
var y,
function f1(a,b){}

Step 2: Execution phase:

x = 5;
y = 6;
f1（5,6）调用函数,执行函数体代码;
函数里面var a = 5;
var b = 6;
a = a+1;//6
b = b+1;//7
返回值

Similarly: complex type data objects are stored in the same way on the stack

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