CODEWITHSUNDEEP
javascriptdictionary
binaryBigInt
binaryBigInt

Reputation: 1704

JavaScript create a dictionary - missing key

If I try to create a dictionary this way:

var dict = [];
$.each(objs, function (idx, obj) {
    dict[obj.category] = obj;
});

Old elements with the same category are overwritten and each key only has one value, if I do it this way:

var dict = [];
$.each(objs, function (idx, obj) {
    dict[obj.category].push(obj);
});

I get an error if the key doesn't exist. How can I solve this problem? I basically want a dictionary which looks like this:

"Category1":{obj1,obj2,obj3},
"Category2":{obj4,obj5,obj6}

Upvotes: 1

Views: 918

Answers (4)

Suren Srapyan
Suren Srapyan

Reputation: 68655

It is good to simulate {} for dictionary, but for dictionary logic it will be better to use Maps to work on higher level of abstraction. Check if the object has a key, if not create and assign to it an array, if already has - just push into it.

const map = new Map();

$.each(objs, function (idx, obj) {

    if(!map.has(obj.category)) {
       map.set(obj.category, []);
    }

    map.get(obj.category).push(obj);

});

Upvotes: 2

Charles
Charles

Reputation: 640

Just use an object.

let dict = {};
dict.Category1 = {};
dict.Category2 = {};
console.log(dict.hasOwnProperty('Category1'), dict.hasOwnProperty('Category3'));

for (item in dict) {
  console.log(item, dict[item]);
}

Upvotes: 0

charlietfl
charlietfl

Reputation: 171669

first off use an object since arrays have numeric indexing

Create an array if the category key doesn't exist

var dict ={};
$.each(objs, function (idx, obj) {
    // if key exists use existing array or assign a new empty array
    dict[obj.category] = dict[obj.category] || [] ;
    dict[obj.category].push(obj);
});

Upvotes: 5

Nina Scholz
Nina Scholz

Reputation: 386570

You could check if the property exists and if not assign an empty array.

Then push the value.

dict[obj.category] = dict[obj.category] || [];
dict[obj.category].push(obj);

Upvotes: 3

Related Questions