Javascript arguments are passed by value

Javascript arguments are passed by value

Base data types in js are stored in stacks:

Js reference data types, variable names and addresses stored in the stack, variable values stored in the heap memory:

Here’s how to pass parameters to a function:

Pass by value

var value = 1;
function foo(v) {
    v = 2;
    console.log(v); / / 2
}
foo(value);
console.log(value) / / 1
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Before the change:

After the change:

When you pass a value to foo, you copy a value. Let’s say the copy is called _value. The function changes the value of _value without affecting the original value.

Pass by reference

var obj = {
    value: 1
};
function foo(o) {
    o.value = 2;
    console.log(o.value); / / 2
}
foo(obj);
console.log(obj.value) / / 2
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Before the change:

After the change:

var obj = {
    value: 1
};
function foo(o) {
    o = 2;
    console.log(o); / / 2
}
foo(obj);
console.log(obj.value) / / 1
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Before the change:

After the change:

Obj. Value = 1 obj. Value = 1 obj. Value = 1 obj. Value = 2

Passing a copy of the reference to the object, i.e. assuming that the memory address of obj is 0011, then the variable O is also stored at that address on the stack. If we assign the constant 2 to O, o is not stored at 0011, but at 2.