小编Ale*_*kin的帖子

我正在研究RXJS并坚持这个问题:运算符"reduce"和"scan"的相同代码以不同的方式工作,但我认为必须返回相同的结果.以下示例.请帮忙.

const txtElement1 = document.getElementById('txt1');
const txtElement2 = document.getElementById('txt2');
const txtElement3 = document.getElementById('txt3');

// function return Observable
function get(array, initValue) {
  return Rx.Observable.create(observer => {
    let timer = initValue;

    array.forEach(item => {
      setTimeout(() => observer.next(item), timer);
      timer += 1000;
    });
  });
}

// 1) don't work with "reduce"
var stream1$ = get(['John', 'Ann', 'Bob'])
  .reduce(function(acc, x) {
    return acc + ` ${x}`;
  }, 'first - ');

stream1$.subscribe(text => txtElement1.innerHTML = text);

// 2)  the same code, but with "scan" - …