JavaScript function parameters: whether to pass the value (byVal) or the address (byRef) Sharing _ javascript skills

This article mainly introduces the misunderstanding of whether the function parameter in JS is to pass the value (byVal) or to transfer the address (byRef). We will explain through examples, if you have any need, you can refer to the common misunderstanding of "whether JavaScript function parameters are byVal or byRef": number, string and other "simple types" are values, Number, String, Object, Array, and other "complex types" are data transfer addresses.
Isn't that true? Why is there such a misunderstanding? Let's take a look at the two codes:

The Code is as follows:

// Code that creates the illusion of passing values
Function modifyLikeByVal (x ){
X = 1;
Console. log ('X = % d', x );
}
Var x = 0;
Console. log ('X = % d', x); // output x = 0
ModifyLikeByVal (x); // output x = 1
Console. log ('X = % d', x); // output x = 0 x not changed!

The Code is as follows:

// Code that creates the illusion of an address transfer
Function modifyLikeByRef (x ){
X [0] = 4;
X [1] = 5;
X [2] = 6;
Console. log ('X = [% s] ', x. join (','));
}
Var x = [1, 2, 3];
Console. log ('X = [% s] ', x. join (', '); // output x = [1, 2, 3]
ModifyLikeByRef (x); // output x = [4, 5, 6]
Console. log ('X = [% s] ', x. join (', '); // output x = [4, 5, 6] x changed!

As a result, the code above concludes that "simple type" is passed as a parameter (byVal), and "complex type" is passed as a parameter (byRef.

What is the problem?

Observe the two functions carefully to find one point:
In byVal, the parameter x: x = 1 is directly modified;
In byRef, x [0] = 4; x [1] = 5; x [2] = 6;

I guess from this: In JavaScript, all variables or members are a pointer. When modifying a variable or member value, the address of the pointer is actually modified.

The above code can be explained as follows:

In "byVal:

The Code is as follows:

Global {// indicates the global scope, and the following indicates the function Scope
Var x = 0; // initialize pointer x and point to number 0
Fun (x ){
X = global. x; // input the global. x parameter. The x pointer address of the fun domain points to the number 0 in the same way as the x pointer address of the global domain.
X = 1; // modify the x pointer address of the fun domain, pointing to the number 1;
} // The fun domain ends. The x pointer in the global domain has not changed.
}

In "byRef:

The Code is as follows:

Global {// indicates the global scope, and the following indicates the function Scope
/*
Initialize pointer x and point to array [1, 2, 3]
In fact, the three members of x are 0, 1, and 2, respectively pointing to 1, 2, and 3;
*/
Var x = [1, 2, 3];
Fun (x ){
X = global. x; // input the global. x parameter. The x pointer address of the fun domain is the same as the x pointer address of the global domain and points to the array [1, 2, 3].
/*
X in the fun domain has not been changed
Then modify the pointer pointing to the three member pointers of x (global. x) in the fun domain.
*/
X [0] = 4;
X [1] = 5;
X [2] = 6;
} // When the fun domain ends, the x pointer in the global domain is not changed, but the three member pointers are changed, so we can see the output result.
}

How can I explain this code ???

The Code is as follows:

(Function (a, B ){
Arguments [0] = 1;
B = 2;
Console. log (arguments, a, B );
}) (-1,-2 );

It can only be said that a, B... is the alias of arguments [0],... [n.

If something is wrong, please point it out. Thank you.

If you have a better explanation, please share it with us.