ecmascript 6 - ES6 for of - is iterable evaluated only once? -
consider simple of: for (const elem of document.getelementsbytagname('*') { // elem } does getelementsbytagname evaluated once or on each iteration ? thx! in case, it's evaluated once obtain iterable , uses obtain iterator . reuses iterator grab values , pass them for block. it's similar doing following generator function: function* getintegers(max) { (let = 0; <= max; i++) { yield i; } } const iterator = getintegers(15); while (true) { const { done, value } = iterator.next(); if (done) { break; } console.log(value); } as noted loganfsmyth , generator functions return iterator directly. note: generator functions can used for..of construct . see this article on mdn more info.
