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Modifying the code

“string”

, the returned value is a string and

typeof

returns

“string”

. A string is also returned when

the second argument is omitted and when the second argument is

“football”

With the conversion function complete, you must modify the rest of the code to use it.

Modifying the code

The first step is to modify the

generateCompareTRs()

function, which now must accept an additional

argument indicating the data type to use when comparing values. Then, the values from the table must

be converted into the appropriate data type within the comparison function:

function generateCompareTRs(iCol, sDataType) {

return function compareTRs(oTR1, oTR2) {

var vValue1 = convert(oTR1.cells[iCol].firstChild.nodeValue,

sDataType);

var vValue2 = convert(oTR2.cells[iCol].firstChild.nodeValue,

sDataType);

//...

};

}

This change to

generateCompareTRs()

once again takes advantage of JavaScript’s support of closures,

passing the

sDataType

argument directly into the comparison function. Unfortunately, you can no

longer use the

localeCompare()

method to return the appropriate function value because numbers

and dates don’t support it. Because you can’t be sure which type of value is being stored, and it doesn’t

make sense to handle each data type’s comparisons differently, it’s best just to use less-than and greater-

than to determine which value to return:

function generateCompareTRs(iCol, sDataType) {

return function compareTRs(oTR1, oTR2) {

var vValue1 = convert(oTR1.cells[iCol].firstChild.nodeValue,

sDataType);

var vValue2 = convert(oTR2.cells[iCol].firstChild.nodeValue,

sDataType);

if (vValue1 < vValue2) {

return –1;

} else if (vValue1 > vValue2) {

return 1;

} else {

return 0;

}

};

}

It may not always be necessary to distinguish between integer and floating-point

values when sorting. Most of the time, simply converting all numbers to floating-

point is sufficient. The code in this chapter uses both types of numbers for illustra-

tive purposes only.

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Sorting Tables

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