I have an object like so:
> Object
> [email protected]: Array[100]
> [email protected]: Array[4]
> 0
id : 132
selected : true
> 1
id : 51
selected : false
etc..
How can I use the underscore _.filter() to return back only the items where selected === true?
I've never had the need to go down to layers with _.filter(). Something like
var stuff = _.filter(me.collections, function(item) {
return item[0].selected === true;
});
Thank you
If you want to pull all array elements from any e-mail address where selected is true, you can iterate like so:
var selected = [];
for (email in emailLists) {
selected.concat(_.filter(emailLists[email], function (item) {
return item.selected === true;
}));
}
If you only want to pull the arrays where all elements are selected, you might instead do something like this:
var stuff = _.filter(me.collections, function(item) {
return _.all(item, function (jtem) {
jtem.selected === true;
});
});
obj should have been emailLists; email is just the key of each element in the object. Where's that error coming up? (I didn't test!) :^)Underscore's filter method will work on an object being used as a hash or dictionary, but it will return an array of the object's enumerable values and strip out the keys. I needed a function to filter a hash by its values that would preserve the keys, and wrote this in Coffeescript:
hash_filter: (hash, test_function) ->
keys = Object.keys hash
filtered = {}
for key in keys
filtered[key] = hash[key] if test_function hash[key]
filtered
If you're not using Coffeescript, here's the compiled result in Javascript, cleaned up a little:
hash_filter = function(hash, test_function) {
var filtered, key, keys, i;
keys = Object.keys(hash);
filtered = {};
for (i = 0; i < keys.length; i++) {
key = keys[i];
if (test_function(hash[key])) {
filtered[key] = hash[key];
}
}
return filtered;
}
hash = {a: 1, b: 2, c: 3};
console.log((hash_filter(hash, function(item){return item > 1;})));
// Object {b=2, c=3}
TL; DR: Object.keys() is great!
_.filter() does. Hope that's cool! :)
_.filter for object with keys is just _.pickI have an object called allFilterValues containing the following:
{"originDivision":"GFC","originSubdivision":"","destinationDivision":"","destinationSubdivision":""}
This is ugly but you asked for an underscore based way to filter an object. This is how I returned only the filter elements that had non-falsy values; you can switch the return statement of the filter to whatever you need:
var nonEmptyFilters = _.pick.apply({}, [allFilterValues].concat(_.filter(_.keys(allFilterValues), function(key) {
return allFilterValues[key];
})));
Output (JSON/stringified):
{"originDivision":"GFC"}
@Dexygen was right to utilize _.pick but a cleaner solution is possible because the function also accepts a predicate
Return a copy of the object, filtered to only have values for the allowed keys (or array of valid keys). Alternatively accepts a predicate indicating which keys to pick.
(highlight is mine)
Here's a real life example I've used in a project
_.pick({red: false, yellow: true, green: true}, function(value, key, object) {
return value === true;
});
// {yellow: true, green: true}
const obj = {
1 : { active: true },
2 : { active: false },
3 : { active: false },
}
let filtered = Object.entries(obj).reduce((acc, current) => {
const currentEntry = current[1];
const currentKey = current[0];
//here you check condition
if (currentEntry.active) {
return {
...acc,
[currentKey]: currentEntry
}
}
return acc;
}, {})
There is a rule of thumb, if you need to achieve something really exotic look up into reducer it can solve almost all problems related to objects, it's a bit tricky to get used to it, but trust me thorough reading of documentation gonna pay off.
Maybe you want a simplest way
_.filter(me.collections, { selected: true})
{selected: true} as a predicate in Underscore, for example with _.filter or _.some. In this case, it is not the whole story because the objects with {selected: true} are embedded in a larger object.
selected == true?