Sample code to assume role and generate temporary credentials using a callback

AWS STS generate credentials using callback.js

const AWS = require('aws-sdk');

const sts = new AWS.STS();
sts.assumeRole({
  DurationSeconds: 3600,
  ExternalId: '1234-1234-1234-1234-1234',
  RoleArn: "Your Role ARN",
  RoleSessionName: 'abc'
}, (err, data) => {
  if (err) throw err;
  console.log(data); // successful response
  }
)