findindex.md

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.

Arguments

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.

Returns

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

Example

/* Found an element */
var array = [1,2,3,4];

var source = Rx.Observable.from(array)
    .findIndex(function (x, i, obs) {
        return x === 1;
    });

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

// => Next: 0
// => Completed

/* 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: ' + x);
    },
    function (err) {
        console.log('Error: ' + err);
    },
    function () {
        console.log('Completed');
    });

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

Location

File:

• /src/core/linq/observable/findindex.js

Dist:

• rx.all.js
• rx.all.compat.js
• rx.aggregates.js

Prerequisites:

• rx.js | rx.compat.js | rx.lite.js | rx.lite.compat.js

NPM Packages:

• rx

NuGet Packages:

• RxJS-All
• RxJS-Aggregates

Unit Tests:

• /tests/observable/findindex.js