Multiple 'If' statements?

Question

Assume i have a function checkTime like the one below where i have to check for multiple condition simultaneously.

var result=0;
function checkTime(time1, time2) {

    if (time1 >= 0 && time2 <= 0) {
        result = 1;
    }
    else if (time1 >= 0 && time2 <= 1) {
        result = 4;
    }
    else if (time1 >= 2 && time2 <= 3) {
        result = 5;
    }
    else if (time1 >= 4 && time2 <= 6) {
        result = 6;
    }
    else if (time1 >= 7 && time2 <= 9) {
        result = 7;
    }
    else if (time1 >= 11 && time2 <= 12) {
        result = 8;
    }
    else if (time1 >= 13 && time2 <= 15) {
        result = 9;
    }
    else if (time1 >= 16 && time2 <= 17) {
        result = 10;
    }
    else if (time1 >= 19 && time2 <= 20) {
        result = 11;
    }
    return result;
}

(The above given example is hypothetical)

The function i have used totally works,but:

Is there a better method or procedure or formula to replace this?(where it doesnt have to be this lengthy or ugly)

Thanx!

You can use OR if multiple conditions would assign the same value to `result`... hypothetically speaking. — Felix Kling, Mar 20 '14 at 03:56
There's generally a better way than a long string of `if` statements, but out of context it's difficult to comment. You hypothetical example doesn't seem to make a lot of sense. — , Mar 20 '14 at 03:57

score 3 · Accepted Answer · answered Mar 20 '14 at 04:00

3

You can use an array to represent all the combination:

tests = [
    { time1: 0, time2: 0, result: 1 },
    { time1: 0: time2: 1, result: 4 },
    ...
];

for (var i = 0; i < tests.length; i++) {
    if (time1 >= tests[i].time1 && time2 <= tests[i].time2) {
        return tests[i].result;
    }
}

answered Mar 20 '14 at 04:00

Barmar

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Your answer looks good,i will see the other answers too before committing to this one. – Nevin Madhukar K Mar 20 '14 at 04:06

score 0 · Answer 2 · answered Mar 20 '14 at 04:01

If the code is identical, and only the values change, you could do something like this:

function checkTime(time1, time2) {
  [
    [0, 0, 0], 
    [0, 1, 0]
  ].forEach(function (it) {
    if (time1 >= it[0] && time2 <= it[1]) {
       return it[2];
    }
  });
}

ngreen · Answer 3 · 2014-03-20T12:50:43.430

0

Well, first off you have the possibility of an undefined result, so that makes things ambiguous. Should result start at 0 instead? This is an important detail. Second, you seem to be working with boundaries, so it would help to change the <= to < to make this clearer. (If so, the 7-9/11-12 section has a bug.) Third, you have an implicit comparison of time1 and time2, so make that explicit.

var result = 0;
var diff = time2 - time1;
var bounds = [21, 19, 16, 13, 11, 7, 4, 2, 0];
if (diff <= 0) result = 0; // unexpected outcome
else
    for (position = 1; position < bounds.length; ++position) {
        if (time1 >= bounds[position]) {
            if (time2 < bounds[position - 1]) {
                result = 3 + (bounds.size - position);
            }
            break;
        }
    }
return result;

Other implementations are possible, but it's hard to tell based on your question exactly what problem you're solving.

follow-up

This section of code has a gap:

else if (time1 >= 7 && time2 <= 9) {
    result = 7;
}
else if (time1 >= 11 && time2 <= 12) {
    result = 8;
}

If time = 10 and time2 = 10, there is no match. It's easy to miss this type of error when you are repeating yourself. Specifying lower and upper bounds for each condition is unnecessary repetition. Since I couldn't see a pattern to the bounds (which could be delegated to a function), I just put the lower bounds into an array and made sure it was sorted descending so that the loop could stop after the first match.

edited Mar 20 '14 at 12:50

answered Mar 20 '14 at 04:26

ngreen

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Its javascript,i have tagged it earlier. :) – Nevin Madhukar K Mar 20 '14 at 04:33
Ok, must be too sleepy and missed the tags. – ngreen Mar 20 '14 at 04:35
1. Result have been set to 0 initially,if that helps. 2. I didnt understand the bug (7-9/11-12) 3. yes making it explicit and coding it is one way of doing it,Implicit comparison is bad? – Nevin Madhukar K Mar 20 '14 at 04:38
In general, I advocate making relationships explicit. In this case, your code assumes that `time2` is always >= `time`, but it does so implicitly. By explicitly comparing the two, the intent is clearer. – ngreen Mar 20 '14 at 04:46
I'm sure the comparator in the loop is wrong, but I may be too tired to fix it at this moment. – ngreen Mar 20 '14 at 05:03
Ahh,so what you were saying was the time gap that i didnt write? well there could be a condition where there shouldn't be any results to be returned in that time gap right? (But nevertheless good practice would be to write the condition and return nothing.) – Nevin Madhukar K Mar 20 '14 at 05:06
Well, I don't know the source of your conditions, so I don't know whether gaps are allowed. I still don't know what sort of problem you're solving. My updated code leaves the result at 0 if `time2` is in a different range from `time1`. – ngreen Mar 20 '14 at 05:15

Multiple 'If' statements?

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