In TypeScript, we use interfaces to group and pass around data. They are used for type checking purposes.
We define an interface as having a property, define its data type, and when the function is called, it validates the data type of the property listed in the interface.
Note: The object that is passed to the function must contain that property (key) that is defined in the interface.
interface LabeledValue {
label: string;
}
function printLabel(labeledObj: LabeledValue) {
console.log(labeledObj.label);
}
let myObj = { size: 10, label: "Size 10 Object" };
printLabel(myObj);
In the above code snippet, we defined an interface LabeledValue
that has one property label
of type string
. When the function PrintLabel
is called, the interface definition will be invoked on myObj
and the data type of label
will be checked.
Here, it is worth noting that properties are not required to be in any order. What matters is the object having property(ies) and data type(s) that an interface requires.
Free Resources