Mutability And Reference VS Privative Types in JavaScript
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Mutability && Primitive && Reference Examples
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### Mutability And Reference VS Privative Types in JavaScript
### Mutability && Primitive && Reference Examples
Mutability
In JavaScript, `String` values are immutable, which means that they cannot be altered once created.
For example, the following code:
var myStr = "Bob";
myStr[0] = "J";
cannot change the value of `myStr` to `Job`, because the contents of `myStr` cannot be altered. Note that this does *not* mean that `myStr` cannot be changed, just that the individual characters of a string literal cannot be changed. The only way to change `myStr` would be to assign it with a new string, like this:
var myStr = "Bob";
myStr = "Job";
### Objects are passed by reference, are mutable, and can be modified by our functions:
function rotateLeft(arr, num) {
for (let i = 0; i < num; i++) {
let el = arr.pop();
arr.unshift(el);
}
}
let myArr = [1, 2, 3, 4, 5, ];
rotateLeft(myArr, 2);
console.log(myArr);
Strings are passed by value, are immutable, and a new array is constructed and returned, because it cannot be changed in place.
function rotateString(str, num) {
return str.slice(num) + str.slice(0, num);
}
let str = "foobar";
let ret = rotateString(str, 3);
console.log(str);
console.log(ret);
### Dereferencing
#### Arrays
To dereference an array, use `let [var1, var2]` syntax.
let arr = ['one', 'two', 'three'];
let [first] = arr;
console.log(first);
#### Objects
To dereference attributes from an object, use `let {}` syntax.
### Primitive Data Types in Depth
### Check Out My New Blog:
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By Bryan Guner on [May 27, 2021](https://medium.com/p/5294422db4b0).
Canonical link
Exported from [Medium](https://medium.com) on September 23, 2021.
