How to iterate over a set in TypeScript?

Question

How do you iterate over a set from TypeScript? for..of does not work:

'Set<string>' is not an array type or a string type 

.forEach unacceptable because it hides this . I would prefer not to do the while loop in the catch try block. What am I missing? Perhaps this is not as awkward as requiring try {while} catch {}.

Answer 1

@SnareChops was basically correct:

 mySet.forEach(function(item){ // do something with "this" }, **this**); 

It works.

I suppose:

 for(item of mySet.values()){ } 

Will work if I don't work with es-shim files that messed up everything for me. But the cushioning material is prescribed by the Angular 2 crew, therefore ¯_ (ツ) _ / ¯

The only thing that worked was:

 for (var item of Arrays.from(set.values())) { } 

or something like that, which is just awful.

Answer 2

You can still use .forEach with the correct this using a regular function instead of the arrow function

 mySet.forEach(function(item){ expect(this).toEqual(item); }); 

Compared with

 class MyClass{ ... doSomething():{ mySet.forEach((item) => { expect(this instanceof MyClass).toEqual(true); }); } } 

Another way of repeating is to use a for loop over values

 for(item of mySet.values()){ ... } 

More information on iterating Set using foreach can be found here.

Answer 3

Extending the highest answer, it is also type safe if we use let for an iteration variable, therefore:

 for (let elem of setOfElems) { ... do anything with elem... } 

This ensures that elem will be of type X if setOfElems been declared as Set<X> .

Answer 4

This worked for me:

 this.mySet.forEach((value: string, key: string) => { console.log(key); console.log(value); }); 

I found it here: Another stack overflow question

Answer 5

You can use for... of in TypeScript if you add "es6" as "lib" in the compiler options and "es6" as the target.

For example (this will be your tsconfig.json):

 { "compilerOptions": { "target": "es6", "lib": [ "es6", "dom" ] }, "exclude": [ "node_modules" ] } 

GitHub related issue: https://github.com/Microsoft/TypeScript/issues/12707