JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test"></div>

JavaScript

var link = [{
  "USER_NAME": "abc",
  "USER_DOB": "10/25/1985",
}, {
  "USER_NAME": "xyz",
  "USER_DOB": "10/25/1986"
}];
for (var i = 0; i < link.length; i++) {
  var tableHeaders = Object.keys(link[i]);
  var newLink = {};

  for (var j = 0; j < tableHeaders.length; j++) {
    var linkKey = tableHeaders[j];
    var formattedStr = linkKey.replace(/_/g, ' ');
    newLink[formattedStr] = link[i][linkKey];
  }
  link[i] = newLink;
}

document.getElementById('test').innerHTML = JSON.stringify(link);