2)Programs in arrow function.js

// a) Print odd number in an array: 
     let arr=[1,2,3,4,5,6,7,8,9,10];
     const oddnum=(arr)=>{
     let result=[];
     for(let v of arr){
         v%2!==0?result.push(v):false;                          //identifying odd number and then insert into the resutl array in this line.
     };
     return result;
     }
     console.log(`Odd number array is: [${oddnum(arr)}]`);
   //  Output array is ===>   Odd number array is: [1,3,5,7,9]

// b)Convert all the strings to title caps in a string array
     let arr1=["deepak","kumar","kishore","lodash","harry"];
     const titlecap=(arr)=>{
         let res=[];
         for(let v of arr){
            res.push(v[0].toUpperCase()+v.slice(1,v.length))    //Changing the first element to caps and added to res array.
     }
     return res;
     }
     console.log(titlecap(arr1));                               //here calling the function and also passing the parameters.
   //   Output array is ===>  Title caped array is : [Deepak,Kumar,Kishore,Lodash,Harry]

// c) Sum of all numbers in an array:
    let arr2=[1,2,3,4,5,6,7,8,9,10];
    const sum_arr=(arr)=>{
          return arr.reduce((a,b)=>a+b,0);                      //one liner for modern js. we are using arrow function to reduce.
    }
    console.log(`Sum of all number in an array is: ${sum_arr(arr2)}`);
   // Output array is ===>    Sum of all number in an array is: 55

// d) Return all prime numbers in an array:
    let arr3=[1,2,3,4,5,6,7,8,9,10];
    let prime_number=(array)=>{                                //function to sort prime numbers.
        let result=[];
        for(let v of array){
            let flag=true;
            if(v>1){
                for(let i=2;i<v;i++){
                    if(v%2===0){
                        flag=false;
                        break;
                    }
                }
            }(flag)? result.push(v):false;                     //Ternary operator.
          }return result;
    }
    let resultvbl=prime_number(arr3);
    console.log(`Prime numbers in an array : [${resultvbl}]`); 
    // Output array is ===>   Prime numbers in an array : [1,2,3,5,7,9]

// e) Return all palindromes in an array:
    let arr4=["did","asddsa","dkdd",123321,121,1234];
    let palindrome=(array)=>{                                 //function to find palindrome in array.
        let res1=[];
        for(let v of array){                                  //for of loop to loop the values.
            v=String(v);
            let l=v.length;
            let tem="";
            for(i=l-1;i>=0;i--){                              //normal for loop in descending order.
                tem+=v[i]
                // console.log(tem);
            }v===tem? res1.push(v):false;
        }
       return res1;
    };
    let z=palindrome(arr4);                                   //storing function output in variable.
    console.log(`Palindrome array is ; [${z}]`);
    //Output array is ===> Palindrome array is ; [did,asddsa,123321,121]