Iterate over set elements

Question

I have turned on the Chrome flag for experimental ECMAscript 6 features, one of which is Set. As I understand, the details of Set are broadly agreed upon by the spec writers.

I create a set a and add the string 'Hello'

a = Set(); a.add('Hello'); 

but how do I iterate over the elements of a?

for(let i of a) { console.log(i); } 

gives "SyntaxError: Illegal let declaration outside extended mode"

for(var i of a) { console.log(i); } 

gives "SyntaxError: Unexpected identifier"

for(var i in a) { console.log(i); } 

gives Undefined

Is it possible to iterate over of a set in Chrome 26?

Answer 1

A very easy way is to turn the Set into an Array first:

let a = new Set(); a.add('Hello'); a = Array.from(a); 

...and then just use a simple for loop.

Be aware that Array.from is not supported in IE11.

Answer 2

Upon the spec from MDN, Set has a values method:

The values() method returns a new Iterator object that contains the values for each element in the Set object in insertion order.

So, for iterate through the values, I would do:

var s = new Set(['a1', 'a2']) for (var it = s.values(), val= null; val=it.next().value; ) {     console.log(val); }