Generic Function in TypeScript

Generic functions are defined by declaring a type parameter when declaring the function ,in angular brackets.The type parameter is the placeholder which is replaced by the actual type arguments when the program executes.

So we define a generic method as:

function GenericFunction<T>(items: T[]): T[] {

The placeholder T above is the type parameter which is replaced by the actual type when the program executes.

So actual value of T could be one of the different data types such number or string.

In the following example we are declaring a GenericFunction which has a type parameter T.Since it is a generic function so it will work with different data types such as number.

In the function we are passing a generic list.We are also returning a list based on the index.So if the index of the list is even then we are including the list element in the returned list.

function GenericFunction<T>(items: T[]): T[] {
var combine: T;
var lst: T[]=[];

for (var i = 0; i <= items.length; i++) {
if(i%2==0)
lst.push(items[i]);
}

return lst;
}

We are calling the above function by passing two different types of lists.A list of strings and a list of numbers.

var lettersList = ['a', 'b', 'c', 'd'];
var filteredLetters = GenericFunction<string>(lettersList);

var numbersList = [1,2,3,4,5,6];
var filteredNumbers = GenericFunction<number>(numbersList);

 

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