Is there a way to insert an item as first element of Set in javascript like it is done in arrays in the example below ?
arr['a','b','c']
arr.unshift ('d')
//Result
arr['d','a','b','c']
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3If the element is already in the set, do you want the old one to stay where it is, or get moved to the front?castletheperson– castletheperson2017-03-31 20:13:28 +00:00Commented Mar 31, 2017 at 20:13
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2 Answers
There is no direct way, or a method to unshift a set element.
You could use the spread syntax ... for the old set and generate a new set.
var mySet = new Set(['a', 'b', 'c']);
mySet = new Set(['d', ...mySet]);
console.log([...mySet]);
Comments
The order of a Set is determined by when the items are inserted. Depending on what you want to do you can either insert items into a Set then extract those values and sort as needed or you can insert them into an array in the correct order then create a Set from that array.
let standardSet = new Set();
standardSet.add('c');
standardSet.add('a');
standardSet.add('b');
let fromStandard = Array.from(standardSet);
fromStandard.sort();
console.log(fromStandard);
let arr = [];
arr.unshift('c');
arr.unshift('b');
arr.unshift('a');
let fromArr = Array.from(new Set(arr));
console.log(fromArr);