[RxJS] Filtering operators: distinct and distinctUntilChanged

最新推荐文章于 2023-04-10 17:29:04 发布

转载最新推荐文章于 2023-04-10 17:29:04 发布 · 77 阅读

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原文链接：http://www.cnblogs.com/Answer1215/p/5543920.html

本文介绍了 RxJS 中的 distinct 运算符及其变种 distinctUntilChanged 的使用方法，通过实例展示了如何通过 distinct 过滤重复项，并且演示了如何通过自定义比较函数和刷新函数来实现更复杂的过滤逻辑。

Operator distinct() and its variants are an important type of Filtering operator. This lessons shows how they work and in what cases are they useful.

distinctUntilChanged():

var foo = Rx.Observable.interval(500).take(5)
  .zip(Rx.Observable.of('a','b','a','a','b'), (x,y)=>y);

/*
--a--b--a--a--b|
   distinctUntilChanged
--a--b--a-----b|
*/

var result = foo.distinctUntilChanged();

result.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);

distinct(comparFn, flushFn):

var foo = Rx.Observable.interval(500).take(5)
  .zip(Rx.Observable.of('a','b','a','a','b'), (x,y)=>y);

/*
--a--b--a--a--b|
   distinct
--a--b---------|
*/

var result = foo.distinct();

result.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);
  
  /*
"next a"
"next b"
"done"  
  */

With CamperFn():

var foo = Rx.Observable.interval(500).take(5)
  .zip(Rx.Observable.of('a','b','a','A','b'), (x,y)=>y);


var comparFn = (x, y) => {
  return x.toLowerCase() === y.toLowerCase();
}

/*
--a--b--a--A--b|
   distinct
--a--b---------|
*/

var result = foo.distinct(comparFn);

result.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);
  
  /*
"next a"
"next b"
"done"  
  */

with FlusherFn:

var foo = Rx.Observable.interval(500).take(5)
  .zip(Rx.Observable.of('a','b','a','A','b'), (x,y)=>y);


var comparFn = (x, y) => {
  return x.toLowerCase() === y.toLowerCase();
}


var flushFn = Rx.Observable.interval(1100).take(1)
  .concat(Rx.Observable.never());

/*
--a--b--a--A--b|
-------0--------
   distinct(comparFn, flushFn)
--a--b--a-----b|
*/

var result = foo.distinct(comparFn, flushFn);

result.subscribe(
  function (x) { console.log('next ' + x); },
  function (err) { console.log('error ' + err); },
  function () { console.log('done'); },
);
  
  /*
"next a"
"next b"
"next a"
"next b"
"done" 
  */

转载于:https://www.cnblogs.com/Answer1215/p/5543920.html