Step 1: Understand the problem

The first step in creating our function is to understand the problem. We are told to calculate the slope of a line given two points. If you remember from high school algebra, the formula to calculate the slope (m) is (y2-y1)/(x2-x1).

//No code needed at this step

Step 2: Define the parameters of the function

Now that we understand what needs to be achieved, we can start creating the code. In javascript, we start by defining our function and the parameters it will take. It will take two points, and each point will have an x and y coordinate.

function calculateSlopeLine(point1, point2) {}

Step 3: Anticipate possible errors

It's always good practice to anticipate possible errors with the inputs. For instance, if the two points have the same x-coordinate, then the slope is undefined. We should take care of these cases.

function calculateSlopeLine(point1, point2) {
  if (point1.x === point2.x) {
    return 'undefined';
  }
}

Step 4: Perform the calculation

Finally, we can now perform the calculation for the slope of line using the coordinates of the two points provided.

function calculateSlopeLine(point1, point2) {
  if (point1.x === point2.x) {
    return 'undefined';
  }
  var slope = (point2.y - point1.y) / (point2.x - point1.x);
  return slope;
}

Step 5: Conclusion

And there we have it, a simple function to calculate the slope of a line given two points. You can now use this function in your code by calling calculateSlopeLine(point1, point2), where point1 and point2 are objects with properties x and y, representing their coordinates on a 2D plane.

function calculateSlopeLine(point1, point2) {
  if (point1.x === point2.x) {
    return 'undefined';
  }
  var slope = (point2.y - point1.y) / (point2.x - point1.x);
  return slope;
}