Problem 3: Taking the following array into consideration get the output as given below:arr = [3,4,5,6,7]Output ==> 3 - 5 - 7Hint: You have to use forEach and conditional statement over here.

Here is a step-by-step solution in JavaScript:

1. First, declare the array:

let arr = [3,4,5,6,7];

2. Initialize an empty string to store the result:

let result = '';

3. Use the forEach method to iterate over the array. Inside the callback function, use an if statement to check if the index of the current element is odd or even. If it's even, add the element to the result string. If it's odd, do nothing:

arr.forEach((element, index) => {
  if (index % 2 === 0) {
    result += element + ' - ';
  }
});

4. The result string now ends with an extra ' - '. Use the slice method to remove it:

result = result.slice(0, -3);

5. Finally, log the result string to the console:

console.log(result);

When you run this code, it will print '3 - 5 - 7' to the console.

Here is a step-by-step solution in JavaScript:

1. First, declare the array:

let arr = [3,4,5,6,7];

2. Initialize an empty string to store the result:

let result = '';

3. Use the forEach method to iterate over the array. In the callback function, check if the index of the current element is even (i.e., the element is at an even position in the array). If it is, add the element to the result string. If it's not the first element, also add a hyphen before the element:

arr.forEach((element, index) => {
    if (index % 2 === 0) {
        result += (result ? ' - ' : '') + element;
    }
});

4. Now, result should contain the desired output:

console.log(result);  // Outputs: "3 - 5 - 7"

Here's the complete code:

let arr = [3,4,5,6,7];
let result = '';
arr.forEach((element, index) => {
    if (index % 2 === 0) {
        result += (result ? ' - ' : '') + element;
    }
});
console.log(result);  // Outputs: "3 - 5 - 7"

This code works by iterating over the array and checking the index of each element. If the index is even, the element is added to the result string. The ternary operator (result ? ' - ' : '') is used to add a hyphen before each element except the first one.