How to prevent automatic sort of Object numeric property?

Question

Why I met this problem: I tried to solve an algorithm problem and I need to return the number which appeared most of the times in an array. Like [5,4,3,2,1,1] should return

Answer 1

target = {}
target[' ' + key] = value // numeric key

This can prevent automatic sort of Object numeric property.

Answer 2

You really can't rely on order of an object fields in JavaScript, but I can suggest to use Map (ES6/ES2015 standard) if you need to preserve order of your key, value pair object. See the snippet below:

let myObject = new Map();
myObject.set('z', 33);
myObject.set('1', 100);
myObject.set('b', 3);

for (let [key, value] of myObject) {
  console.log(key, value);
}
// z 33
// 1 100
// b 3

Answer 3

You are using a JS object, that by definition does not keep order. Think of it as a key => value map.

You should be using an array, that will keep whatever you insert on the index you inserted it into. Think of it as a list.

Also notice that you did not in fact "reverse the order of the assignment", because you inserted elements on the same index every time.

Answer 4

I've stumbled with this issue with our normalised array which keyed with Ids> After did my research, I found out there's no way to fix using the object keys because by default the Javascript is sorting any object key with number when you iterate it.

The solution I've done and it worked for me is to put a 'sortIndex' field and used that to sort the list.