比较函数

function createComparisonFunction(propertyName) {
return function(obj1, obj2) {
var value1 = obj1.getAttribute(propertyName),
value2 = obj2.getAttribute(propertyName);
if (value1 < value2) {
return -1;
} else if (value1 > value2) {
return 1;
} else {
return 0;
}
}
}