如何在时间表中保持领先零

Question

I've got a selection of times, but I want to keep the leading zero:

var fastTrainReading = [0943, 0957, 1006, 1013 , 1027, 1036, 1043, 1057, 1106, 1113, 1127, 1136, 1213, 1227, 1236, 1243, 1257, 1306, 1313, 1327, 1336, 1343, 1357, 1406, 1413, 1427, 1436, 1443, 1457, 1506, 1513, 1527, 1537, 1543, 1559, 1606, 1613, 1627, 1636, 1643, 1657, 1704, 1718, 1728, 1735, 1749, 1758, 1816, 1830, 1847, 1859, 1906, 1911, 1930, 1936, 1941, 1959, 2006, 2017, 2027];

This is the math performed:

var currentTime = hour*100 + mins;
if ((day == 0) || (day == 6)) {
    document.write ("There are no buses today");
}  else {

var displayCount = 0;
        var TrainStr1 = "";
        for (var i=0, len=fastTrainReading.length; i<len; ++i) {
            if ((fastTrainReading[i] > currentTime) && (displayCount < 2)) {
                displayCount = displayCount+1;
                TrainStr1=TrainStr1 + fastTrainReading[i] + "<br/>";
            }
        }
    }
document.write (TrainStr1)

I had a pretty good search through, if I missed something feel free to abuse me (but point me in the right direction).

Answer 1

Simplest solution is to store your time data as strings eg var fastTrainReading = ['0943', ... . JavaScript will cast to integer for you in your calculation routines.

For a comprehensive string formatting solution that adheres to conventional principles, try sprintf() for javascript: http://www.diveintojavascript.com/projects/javascript-sprintf

Answer 2

You can try to use .toString()
like:
TrainStr1=TrainStr1 + fastTrainReading[i].toString() + "<br/>";
alt to save your times as strings.

Answer 3

By default you won't get the leading zeroes.

As you know the length of TrainStr1 is 4, you can use the following function to get zeroes.

function formatted(time) {
    var s = "0000" + time;
    return s.substr(s.length-4); }

You can call the function 'formatted' before using document.write

Answer 4

You need to zero pad your numbers.

Number.prototype.zf = function _zeroFormat(digits)
{
    var n = this.toString(), pLen = digits - n.length;
    for ( var i = 0; i < pLen; i++)
    {
        n = '0' + n;
    }
    return n;
}

if ((fastTrainReading[i] > currentTime.zf(4)) && (displayCount < 2)) {
   displayCount = displayCount+1;
   TrainStr1=TrainStr1 + fastTrainReading[i] + "<br/>";
}

Once you've normalized all of your numbers to be 0-padded to 4 digits, string comparison is possible. Otherwise, you'll have issues. As things stand, it looks like your code was trying to compare a string (like an element from fastTrainReading) and a number (currentTime).

Answer 5

Just declare your array as strings:

var fastTrainReading = ['0943', '0957', '1006', '1013'];

And don't worry fastTrainReading[i] > currentTime will still work. '100' > 99 == true