How to use Underscore.js filter with an object?

问题:

I have an object like so:

> Object   > Rett@site.com: Array[100]   > pel4@gmail.com: 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

回答1:

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;     }); }); 

回答2:

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!

回答3:

I 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"} 

回答4:

Maybe you want a simplest way

_.filter(me.collections, { selected: true}) 

文章来源: How to use Underscore.js filter with an object?