JSFiddle - React, Tailwind, and code Playground

JavaScript

function getPossiblepairs(input, diff){
    // Create a copy of the original array, so it is not affected by the next operation
    var sortedInput = input.slice();
    // Sort the array
    sortedInput.sort();
    // Iterate through the array, starting from the 0th element
    for (var i=0, n=sortedInput.length; i<n; i++){
        firstNumber = sortedInput[i];
        // Iterate through the array, starting from the (i+1)th element
        for (var j=i+1; j<n; j++){
            secondNumber = sortedInput[j];
            // if it matches, then log it!
            if (secondNumber - firstNumber == diff){
                console.log('(' + firstNumber + ', ' + secondNumber + ')');
                break;
            }
        }
    }
}

getPossiblepairs([1,5,3,4,2], 2);
// getPossiblepairs([12, 15, 14, 10, 9, 6, 4], 2);