PSI Conversions SA-5015 jira has details

psicalc.js

function calcPsi(read, loc) {
  const readVal = read.v * read.mul;
  const h = loc.elevation + loc.elevationOffset;
  
  return calcPsiDirect(read.m, h, readVal);
}

function calcPsiDirect(uom, h, readVal){
  let newVal = -1;
  switch (uom) {
    case "PSIA":
      newVal = readVal - (PsiPascElev(h) * 0.000145033);
      break;
    case "PSI":
      newVal = readVal;
      break;
    case "BARA":
      newVal = readVal - (PsiPascElev(h) * Math.pow(10, -5));
      break;
    case "BAR":
      newVal = readVal * 14.5038;
      break;
  } //end-switch

  return newVal;
}
function PsiPascElev(h) {
  let beforeExp = (1 - (2.25577 * Math.pow(10, -5) * h));
  return Math.pow(beforeExp, 5.25588) * 101325;
}


let readRec = {
  "v": 207.6,
  "inputId": 2,
  "mul": 1,
  "m": "PSIA"
};

let loc = {
  "lat": 35.86583,
  "lng": -78.85754,
  "elevation": 108,
  "elevationOffset": -1.2192
};

let psi = calcPsi(readRec, loc);

console.log(psi);