const inputBody = '{
  "type": "object",
  "properties": {
    "params": {
      "type": "object",
      "required": [
        "number"
      ],
      "properties": {
        "number": {
          "type": "string",
          "description": "Sales estimate number to check"
        }
      }
    }
  }
}';
const headers = {
  'Content-Type':'application/json',
  'Accept':'application/json'
};

fetch('https://goldleaf.app/api/v1/salesestimates/checkexisting',
{
  method: 'POST',
  body: inputBody,
  headers: headers
})
.then(function(res) {
    return res.json();
}).then(function(body) {
    console.log(body);
});