Math.ceil vs Math.floor

Every now and then I come across calls to the ceil and floor methods, belonging to Math. Both methods aim to round a floating point number to an integer number. However, a question that always comes to me, almost automatically, is:

After all, would there be any way to visually compare the logic of these two functions?

Good... Let me try.

Let's imagine that there is a graph in which we can place each argument passed to these functions:

Math.ceil(num)

It has the function of rounding a number to the nearest integer value, greater than or equal to (>=) the current number.

num === 1.3

Looking at the number inserted in the graph above, what would be the closest integer >= to 1.3? The number 2, of course!

num === -2,001

Looking at the number inserted in the graph above, what would be the closest integer >= to -2.001? Since we are now dealing with a negative scale, the next integer >= is -2.

Math.floor(num)

It has the function of rounding a number to the nearest integer value, less than or equal (<=) to the current number. In short, it works the same as Math.ceil, but in the opposite direction on the graph.

num === 1.3

Looking at the number inserted in the graph above, what would be the closest integer <= to 1.3? The number 1, of course!

num === -2,001

Looking at the number inserted in the graph above, what would be the closest integer <= to -2.001? Since we are now dealing with a negative scale, the next integer <= is -3.

Thus, analyzing the sense of rounding these functions and taking the graph into consideration, we have:

Remembering concepts using images (like the one mentioned above) usually helps me a lot in fixing them. ?​

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