The case is simple - I've got a following object:
Object {1: false, 2: true, 3: false, 4: false, 5: false, 6: false, 7: false, 8: true, 12: false, 13: false, 14: false, 15: false, 16: false, 17: false, 18: false, 19: false}
and I need to get an array of ids that had true value, using underscore. In above case that would be:
[2, 8]
I tried few things but I'm a bit stuck. Does anyone have any idea?
var keys = [];
_.each( obj, function( val, key ) {
if ( val ) {
keys.push(key);
}
});
There may be easier/shorter ways using plain Underscore.
In case anyone here uses Lodash instead of Underscore, the following is also possible, which is very short and easy to read :
var keys = _.invert(obj, true)[ "true" ];
Giorgi Kandelaki gave a good answer, but it had some potential problems (see my comment on his answer).
The correct way is:
_(obj).pairs().filter(_.last).map(_.first)
or
_.map(_.filter(_.pairs(obj),_.last),_.first)
var data = {1: false, 2: true, 3: false, 4: true};
var filteredIds = _.filter(_.keys(data), function (key) {
return data[key];
});
// result [2, 4]
var rejectedIds = _.reject(_.keys(data), function (key) {
return data[key];
});
// result [1, 3]
You can use _.pick
. Like this:
var data = {1: false, 2: true, 3: false, 4: false, 5: false, 6: false, 7: false, 8: true, 12: false, 13: false, 14: false, 15: false, 16: false, 17: false, 18: false, 19: false}
var keys = _.keys(_.pick(data, function(value) {
return value;
}));
You can try this:
_.pairs(obj)
.filter(function(pair) { return pair[1] })
.map(function(pair) { return pair[0] })
Or the same but bit more concise:
_.pairs(obj).filter(_.last).map(_.first)
var obj = {1: false, 2: true /*...*/};
you can use reduce:
_(obj).reduce(function(memo, val, key){
if (val)
memo.push(key);
return memo;
}, []);
or chain map:
_(obj).chain().map(function(val, key){
if (val)
return key;
}).reject(_.isUndefined).value();
You can do it very easily
var obj = { a: false, b: false, c: true, d: false, e: true, f: false };
name, names;
name = _.findKey(obj, true);
// -> 'c'
names = _.findKeys(obj, true);
// -> ['c', 'e']
For that you juste need to extend underscore a little :
_.mixin({
findKey: function(obj, search, context) {
var result,
isFunction = _.isFunction(search);
_.any(obj, function (value, key) {
var match = isFunction ? search.call(context, value, key, obj) : (value === search);
if (match) {
result = key;
return true;
}
});
return result;
},
findKeys: function(obj, search, context) {
var result = [],
isFunction = _.isFunction(search);
_.each(obj, function (value, key) {
var match = isFunction ? search.call(context, value, key, obj) : (value === search);
if (match) {
result.push(key);
}
});
return result;
}
});
And you can even use a function as filter, like this :
var team = {
place1: { name: 'john', age: 15 },
place2: { name: 'tim', age: 21 },
place3: { name: 'jamie', age: 31 },
place4: { name: 'dave', age: 17 }}
// Determine the places of players who are major
var placeNames = _.findKeys(team, function(value) { return value.age >= 18; });
// -> ['place2', 'place3']
Enjoy ;-)
My version:
var list = {
1: false, 2: true, 3: false, 4: false,
5: false, 6: false, 7: false, 8: true,
12: false, 13: false, 14: false, 15: false,
16: false, 17: false, 18: false, 19: false
};
_.chain(list).map(function(val, key) {
return val ? parseInt(key) : undefined
}).reject(function(val) {
return _.isUndefined(val);
}).value();
// returns [2,8]
This might be easier
result = _.chain(obj)
.map(function(value, key){
return value?key:false;
})
.filter(function(v){
return v
})
.value();
function findKey(obj, value){
var key;
_.each(_.keys(obj), function(k){
var v = obj[k];
if (v === value){
key = k;
}
});
return key;
}
Another potential solution:
// Your example data
var data = {1: false, 2: true, 3: false, 4: false, 5: false, 6: false, 7: false, 8: true, 12: false, 13: false, 14: false, 15: false, 16: false, 17: false, 18: false, 19: false};
// Outputs the keys: ["2", "8"]
_.keys(_.transform(data, function(r, v, k) { v ? r[k] = 1 : null; }));
// Outputs the keys as integers: [2, 8]
_.map(_.keys(_.transform(data, function(r, v, k) { v ? r[k] = 1 : null; })), _.parseInt)
So basically:
I use this one: Retrieve all keys with the same value from an object (not only an object with just boolean values) using lodash
function allKeys(obj, value) {
_.keys(_.pick(obj, function (v, k) { return v === value; }));
}
Example:
var o = {a: 3, b: 5, c: 3};
var desiredKeys = allKeys(o, 3);
// => [a, c]
Heres a way to do it without using any libraries in ES6
let z = {2: true, 3:false, 8:true, 9:false, 10: false}
Array.from(new Set(Object.keys(z).map(function(k){if(z[k]){return k}}))).filter(f=>f)
and out you get [2, 8]
I Do not know underscore.js
. But using normal JS, I have written the below code.
function myFunction()
{
var str="1: false; 2: true; 3: false; 4: false; 5: false; 6: false; 7: false; 9: true; 12: false";
var n=str.split(";");
for(var i=0;i<n.length;i++)
{
if(n[i].search("true")!=-1){
alert(n[i].slice(0,n[i].search(":")));
}
}
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