Is it possible to sort the entries of a es6 map object?
var map = new Map();
map.set('2-1', foo);
map.set('0-1', bar);
results in:
map.entries = {
0: {"2-1", foo },
1: {"0-1", bar }
}
Is it possible to sort the entries based on their keys?
map.entries = {
0: {"0-1", bar },
1: {"2-1", foo }
}
14 Answers
According MDN documentation:
A Map object iterates its elements in insertion order.
You could do it this way:
var map = new Map();
map.set('2-1', "foo");
map.set('0-1', "bar");
map.set('3-1', "baz");
var mapAsc = new Map([...map.entries()].sort());
console.log(mapAsc)Using .sort(), remember that the array is sorted according to each character's Unicode code point value, according to the string conversion of each element. So 2-1, 0-1, 3-1 will be sorted correctly.
Short answer
new Map([...map].sort((a, b) =>
// Some sort function comparing keys with a[0] b[0] or values with a[1] b[1]
))
If you're expecting strings: As normal for .sort you need to return -1 if lower and 0 if equal; for strings, the recommended way is using .localeCompare() which does this correctly and automatically handles awkward characters like ä where the position varies by user locale.
So here's a simple way to sort a map by string keys:
new Map([...map].sort((a, b) => String(a[0]).localeCompare(b[0])))
...and by string values:
new Map([...map].sort((a, b) => String(a[1]).localeCompare(b[1])))
These are type-safe in that they won't throw an error if they hit a non-string key or value. The String() at the start forces a to be a string (and is good for readability), and .localeCompare() itself forces its argument to be a string without hitting an error.
