pass by value or pass by reference?

pass.js

'use strict'

let func = (a, b, c) => {
    a = "a-new-value"
    b = b + "+ b-new-value"
    c[0] = "c-new-value1"
}

let a = "a-old-value"
let b = "b-old-value"
let c = ["c-old-value1", "c-old-value2"]

func(a, b, c)

console.log(a, b, c) // a-old-value b-old-value [ 'c-new-value1', 'c-old-value2' ]

pass.py

def func(a, b, c):
    a = "a-new-value"
    b = b + "+ b-new-value"
    c[0] = "c-new-value1"

a = "a-old-value"
b = "b-old-value"
c = ["c-old-value1", "c-old-value2"]

func(a, b, c)

print(a, b, c) # a-old-value b-old-value ['c-new-value1', 'c-old-value2']

pass.rb

def func(a, b, c)
    a = "a-new-value"
    b = b + "+ b-new-value"
    c[0] = "c-new-value1"
end

a = "a-old-value"
b = "b-old-value"
c = ["c-old-value1", "c-old-value2"]

func(a, b, c)

puts(a, b, c)   # a-old-value
                # b-old-value
                # c-new-value1
                # c-old-value2