Send XMLHttpRequest

function reqListener () {
  console.log(this.responseText);
}
function admobReport() {
var url = 'https://content.googleapis.com/adsense/v1.4/accounts/';
var accountId = 'pub-xxx'; // change to your own accountId
url += accountId;  
url += '/reports?dimension=APP_ID';
url += '&filter=AD_CLIENT_ID==ca-app-' + accountId;
url += '&metric=EARNINGS'
url += '&startDate=2018-02-01';  // change start date
url += '&endDate=2018-02-24'; // change end date
var oReq = new XMLHttpRequest();
oReq.addEventListener("load", reqListener);
oReq.open("GET", url);
var AuthorizationToken = 'xxx';  // The way to get it is in this post
oReq.setRequestHeader('Authorization', 'AuthorizationToken');
oReq.send();
}
admobReport();

Response

{
 "kind": "adsense#report",
 "totalMatchedRows": "1",
 "headers": [
  {
   "name": "APP_ID",
   "type": "DIMENSION"
  },
  {
   "name": "EARNINGS",
   "type": "METRIC_CURRENCY",
   "currency": "USD"
  }
 ],
 "rows": [
  [
   "2:com.westminstershortercatechismqa",
   "0.89"
  ]
 ],
 "totals": [
  "",
  "0.89"
 ],
 "averages": [
  "",
  "0.89"
 ],
 "startDate": "2018-02-01",
 "endDate": "2018-02-24"
}

We can get the total earnings are 0.89$.

accountId

Just login into your AdSense home page, you will found it.

AuthorizationToken

Generate Authorization Header at first.
You have to login your AdSense account and grant authorization access.

Press F12 to open developer tool in your browser.
Press "EXECUTE" button again.
Then you will find the Authorization Header.

Remember this Header value and keep it secrect.
Replace the value to the JS code at the begining.
Then you can get your AdMob earnings via just one HTTP get API in any place.

Refers

AdSense Management API
AdMob Reporting
AdSense Management API Get Started