While working with MochiKit I've accumulated a bunch of helper methods.
It's possible that there is already a better way to do some of these
things, which I'd be grateful to learn. Anyway, feel free to adopt or
improve them if they seem useful.
1) I discovered that if you Base.clone an object then try to delete a
property it doesn't work as expected (the copy-on-write magic of clone
makes this impossible). Here is an eagerly copying version, which uses
a subset helper method which is useful in its own right:
function eagerClone(obj) {
return subset(obj, MochiKit.Base.keys(obj));
}
function subset(obj, keys) {
var copy = {};
for (var i in keys) {
var key = keys[i];
copy[key] = obj[key];
}
return copy;
}
2) I use Base.keys all the time, so the lack of a values method was
surprising:
function values(obj) {
return MochiKit.Base.map(function(x) { return obj[x] },
MochiKit.Base.keys(obj));
}
3) Similarly, a way to reverse the effect of Base.items is useful. With
it you can write methods to "map" just the values of an object:
function objectFromItems(items) {
var obj = {};
for (var i in items) {
var item = items[i];
obj[item[0]] = item[1];
}
return obj;
}
function mapItems(fn, obj) {
return objectFromItems(MochiKit.Base.map(fn,
MochiKit.Base.items(obj)));
}
function mapValues(fn, obj) {
return mapItems(function(item) {
return [item[0], fn(item[1], item[0])];
}, object);
}
4) This one is a little more random--rotating an array in either
direction:
function rotateArray(array, amount) {
if (amount > 0)
pushAll(array, array.splice(0, amount));
else if (amount < 0)
unshiftAll(array, array.splice(array.length + amount, -amount));
}
function pushAll(dest, array) {
Array.prototype.push.apply(dest, array);
}
function unshiftAll(dest, array) {
Array.prototype.unshift.apply(dest, array);
}
Thanks,
Chris
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