TypeScript: Type System
A brief introduction to “Data Immutability” in TypeScript
In this lesson, we are going to learn a few techniques to make values immutable, both at compile-time and at runtime.
JavaScript is not so strong when it comes to data immutability. Internally, all primitive data types like string, number, boolean etc. are immutable which means you can’t mutate the value once it is set to a variable. You can only assign a new value to a variable and the old one will be garbage collected by the JavaScript engine when the time comes.
That’s not the same story with objects. If you create a plain object using an object literal, you can override the value of a property or add or remove a property to or from an object whenever you want.
var obj = {a: 1}; // define an object
obj.b = 2; // add new property
obj.c = 'hello'; // add new propertyobj.b = 3; // update property value
delete obj.b; // delete property
Objects are by default mutable as shown above and they are passed by reference (but not in a way that operates in other languages). When you assign an object to a variable, the object value doesn’t get copied. JavaScript only assigns a reference of the object to the new…
