underscore.js的排序扩展。 倒序和多列排序

// Sort the object's values by a criterion produced by an iterator.
_.sortBy = function (obj, iterator, context) {
iterator = lookupIterator(iterator, context);
return _.pluck(_.map(obj, function (value, index, list) {
return {
value: value,
index: index,
criteria: iterator(value, index, list)
};
}).sort(function (left, right) {
var a = left.criteria;
var b = right.criteria;
if (a !== b) {
if (a > b || a === void 0) return 1;
if (a < b || b === void 0) return -1;
}
return left.index - right.index;
}), 'value');
};
// Sort the object's values by a criterion produced by an iterator.
_.sortByDesc = function (obj, iterator, context) {
iterator = lookupIterator(iterator, context);
return _.pluck(_.map(obj, function (value, index, list) {
return {
value: value,
index: index,
criteria: iterator(value, index, list)
};
}).sort(function (left, right) {
var a = left.criteria;
var b = right.criteria;
if (a !== b) {
if (a > b || a === void 0) return -1;
if (a < b || b === void 0) return 1;
}
return left.index - right.index;
}), 'value');
};

_.multisortBy = function (obj, iterator, context) {
return _.pluck(
_.map(obj, function (value, index, list) {
return {
value: value,
criteria: iterator.call(context, value, index, list)
}
}).sort(function (left, right) {
var a = left.criteria, b = right.criteria;
if (!$.isArray(a)) {
return a < b ? -1 : a > b ? 1 : 0;
} else {
var result = 0;
for (var i = 0 ; i < a.length ; i++) {
var r = a[i] < b[i] ? -1 : a[i] > b[i] ? 1 : 0;
if (r != 0 || i == a.length - 1)
return r;
}
}
}), 'value');
}