Typescript

gistfile1.txt

//declare a function type
type inbound = (val1:number,val2:number)=>number;

//function with callback
function operation(val1:number,val2:number,callback:(num1:number,num2:number)=>number):number{
    return callback(val1,val2);
}

let multiplication = operation(15,3,(value1,value2)=>value1*value2);

let sum = operation(15,3,(value1,value2)=>value1 + value2);

//function with callback
let  demoCallback = (val1:number,val2:number,callback:inbound):number=>{
    return callback(val1,val2);
}

const total = demoCallback(15,3,(value1,value2)=>value1*value2);

console.log(total);

function greeter(firstName:string,lastName:string,greetMe:(val1:string,val2:string)=>string):string{
    return greetMe(firstName,lastName);
}

let greeted = greeter('sole','dogan',(val1,val2)=>val2  + val1 )