Beginning Angular 2 with Typescript by Greg Lim

Author:Greg Lim [Lim, Greg]
Language: eng
Format: epub, pdf
Published: 2017-02-05T08:00:00+00:00

filter Operator

In our input, say we want to call Spotify only if the user types at least three characters so as not to flood Spotify with too many requests. To do so, we can apply the filter operator. We do so by first importing the filter operator with the below code

import 'rxjs/add/operator/filter';

and add the filter operator as shown below in bold.

this.searchControl.valueChanges

.filter(text => text.length >= 3)

.subscribe(value => {

console.log(value);

});

The filter operator takes an expression text.length >= 3 and determines that the value should be selected only if the expression returns true. filter then returns another Observable that we can either subscribe to or apply another operator. If we run the app now, we see only text of length greater or equal to three logged in the console.

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