Parameter-object in JavaScript

Objects, unlike primitives, are passed by reference. This means that changing an object inside the function will cause it to change outside the function as well. See an example:

function func(arr) {
	arr[0] = '!';
}

let arr = [1, 2, 3];
func(arr);
console.log(arr); // shows ['!', 2, 3]

Determine what will be output to the console without running the code:

function func(obj) {
	obj.a = '!';
}

let obj = {a: 1, b: 2, c: 3};
func(obj);
console.log(obj);

Determine what will be output to the console without running the code:

function func(arg) {
	arg = '!';
}

let obj = {a: 1, b: 2, c: 3};
func(obj.a);
console.log(obj);

Determine what will be output to the console without running the code:

function func(obj) {
	obj = '!';
}

let obj = {a: 1, b: 2, c: 3};
func(obj.a);
console.log(obj);

Determine what will be output to the console without running the code:

function func(arr) {
	arr.splice(1, 1);
}

let arr = [1, 2, 3];
func(arr);
console.log(arr);

Determine what will be output to the console without running the code:

function func(arr) {
	arr.slice(1, 1);
}

let arr = [1, 2, 3];
func(arr);
console.log(arr);

Determine what will be output to the console without running the code:

function func(arr) {
	let newArr = arr;
	newArr[0] = '!';
}

let arr = [1, 2, 3];
func(arr);
console.log(arr);