How can I union arrays inside an array using lodash?
For example:
Input:
var x = [ [1,2,3,4], [5,6,7], [], [8,9], [] ];Expected output:
x = [1,2,3,4,5,6,7,8,9];
Currently my code does the following:
return promise.map(someObjects, function (object)) {
return anArrayOfElements();
}).then(function (arrayOfArrayElements) {
// I tried to use union but it can apply only on two arrays
_.union(arrayOfArrayElements);
});
Use apply method to pass array values as arguments:
var union = _.union.apply(null, arrayOfArrayElements);
this (see. apply definition).The simplest solution I can think of is to just use concat:
Array.prototype.concat.apply([], [ [1,2,3,4], [5,6,7],[], [8,9], []]);
Will produce...
[ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
Concat not remove duplicate items instead lodash union.
Worked answer for me , all other answers worked but when i checked other post they simply used loadash. I dnt know what is the best syntax to use for all the answers provided in the post. For now using the below method
_.uniq(_.flatten(x)); // x indicates arrayOfArrayObjects
// or, using chain
_(x).flatten().uniq().value();
Thanks everyone for their answers. :)
Just reduce it using the native function reduce
arr.reduce(function(previousValue, currentValue) {
return previousValue.concat(currentValue);
}, []);
This will apply the reduce callback function to each element of the array and reduce it for the use case you have shown.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
_.flatten?