I have a dictionary that has the format of
dictionary = {0: {object}, 1:{object}, 2:{object}}
How can I iterate through this dictionary by doing something like
for ((key, value) in dictionary) { //Do stuff where key would be 0 and value would be the object }
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Answer
tl;dr
- In ECMAScript 2017, just call
Object.entries(yourObj)
. - In ECMAScript 2015, it is possible with
Map
s. - In ECMAScript 5, it is not possible.
ECMAScript 2017
ECMAScript 2017 introduced a new Object.entries
function. You can use this to iterate the object as you wanted.
'use strict'; const object = {'a': 1, 'b': 2, 'c' : 3}; for (const [key, value] of Object.entries(object)) { console.log(key, value); }
Output
a 1 b 2 c 3
ECMAScript 2015
In ECMAScript 2015, there is not Object.entries
but you can use Map
objects instead and iterate over them with Map.prototype.entries
. Quoting the example from that page,
var myMap = new Map(); myMap.set("0", "foo"); myMap.set(1, "bar"); myMap.set({}, "baz"); var mapIter = myMap.entries(); console.log(mapIter.next().value); // ["0", "foo"] console.log(mapIter.next().value); // [1, "bar"] console.log(mapIter.next().value); // [Object, "baz"]
Or iterate with for..of
, like this
'use strict'; var myMap = new Map(); myMap.set("0", "foo"); myMap.set(1, "bar"); myMap.set({}, "baz"); for (const entry of myMap.entries()) { console.log(entry); }
Output
[ '0', 'foo' ] [ 1, 'bar' ] [ {}, 'baz' ]
Or
for (const [key, value] of myMap.entries()) { console.log(key, value); }
Output
0 foo 1 bar {} baz
ECMAScript 5:
No, it’s not possible with objects.
You should either iterate with for..in
, or Object.keys
, like this
for (var key in dictionary) { // check if the property/key is defined in the object itself, not in parent if (dictionary.hasOwnProperty(key)) { console.log(key, dictionary[key]); } }
Note: The if
condition above is necessary only if you want to iterate over the properties which are the dictionary
object’s very own. Because for..in
will iterate through all the inherited enumerable properties.
Or
Object.keys(dictionary).forEach(function(key) { console.log(key, dictionary[key]); });