Let's assume that we have following generator:
var gen = function* () {
for (var i = 0; i < 10; i++ ) {
yield i;
}
};
What is the most efficient way to loop through the iterator ?
Currently I do it with checking manually if done property is set to true or not:
var item
, iterator = gen();
while (item = iterator.next(), !item.done) {
console.log( item.value );
}
The best way to iterate any iterable (an object which supports @@iterator), is to use for..of, like this
'use strict';
function * gen() {
for (var i = 0; i < 10; i++) {
yield i;
}
}
for (let value of gen()) {
console.log(value);
}
Or, if you want an Array out of it, then you can use Array.from, like this
console.log(Array.from(gen());
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
const value of gen() triggers an error in Firefox 42 (SyntaxError: invalid for/in left-hand side). let value of gen() works.
let to be recognized. In "plain" JavaScript mode, neither const value of, nor let value of work (but var value of does).A self-contained, single-line alternative to the while loop in the question is the for loop. And for the special case of iterating through for pure side effect or depletion, rather than doing something with the results at the end, we avert the issue of binding the next item value, then not using it in a for-of solution:
for (let n = iterator.next(); !n.done; n = iterator.next()) {}
iterator.next().valueiterator.next().done..so it should beitem().valueanditem().done