Rx.Observable.prototype.findIndex(predicate, [thisArg])

Searches for an element that matches the conditions defined by the specified predicate, and returns the first occurrence within the entire Observable sequence.

参数

1. predicate (Function): A function to test each source element for a condition; The callback is called with the following information:
   1. the value of the element
   2. the index of the element
   3. the Observable object being subscribed
2. [thisArg] (Any): Object to use as this when executing the predicate.

返回值

(Observable): An Observable sequence with the first element that matches the conditions defined by the specified predicate, if found; otherwise, undefined.

例

/* Not found */
var array = [1,2,3,4];

var source = Rx.Observable.from(array)
  .findIndex(function (x, i, obs) { return x === 5; });

var subscription = source.subscribe(
  function (x) {
    console.log('Next: %s', x);
  },
  function (err) {
    console.log('Error: %s', err);
  },
  function () {
    console.log('Completed');
  });

// => Next: -1
// => Completed