docs(prometheus-exporter): fix prometheus exporter examples in README (…

…open-telemetry#3110)


Co-authored-by: Daniel Dyla <[email protected]>

experimental/packages/opentelemetry-api-metrics/README.md

@@ -38,12 +38,12 @@ const api = require("@opentelemetry/api-metrics");
 const { MeterProvider } = require("@opentelemetry/sdk-metrics");
 const { PrometheusExporter } = require("@opentelemetry/exporter-prometheus");
 
-const meterProvider = new MeterProvider({
-  // The Prometheus exporter runs an HTTP server which
-  // the Prometheus backend scrapes to collect metrics.
-  exporter: new PrometheusExporter({ startServer: true }),
-  interval: 1000,
-});
+// The Prometheus exporter runs an HTTP server which the Prometheus backend
+// scrapes to collect metrics.
+const exporter = new PrometheusExporter({ startServer: true });
+// Creates MeterProvider and installs the exporter as a MetricReader
+const meterProvider = new MeterProvider();
+meterProvider.addMetricReader(exporter);
 
 /**
  * Registering the provider with the API allows it to be discovered

experimental/packages/opentelemetry-exporter-prometheus/README.md

@@ -26,11 +26,10 @@ const { MeterProvider }  = require('@opentelemetry/sdk-metrics');
 const options = {port: 9464, startServer: true};
 const exporter = new PrometheusExporter(options);
 
-// Register the exporter
-const meter = new MeterProvider({
-  exporter,
-  interval: 1000,
-}).getMeter('example-prometheus');
+// Creates MeterProvider and installs the exporter as a MetricReader
+const meterProvider = new MeterProvider();
+meterProvider.addMetricReader(exporter);
+const meter = meterProvider.getMeter('example-prometheus');
 
 // Now, start recording data
 const counter = meter.createCounter('metric_name', {