problem with request: unable to verify the first certificate

[Prabhat-Sutar]

I am using "paypal-rest-sdk": "1.8.1", I am getting this error:

problem with request: unable to verify the first certificate error { Error: unable to verify the first certificate at TLSSocket.<anonymous> (_tls_wrap.js:1116:38) at emitNone (events.js:106:13) at TLSSocket.emit (events.js:208:7) at TLSSocket._finishInit (_tls_wrap.js:643:8) at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:473:38) code: 'UNABLE_TO_VERIFY_LEAF_SIGNATURE' }

Here is my code:

`
var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var paypal = require('paypal-rest-sdk');

app.use(bodyParser.urlencoded({ extended: false }))

console.log(__dirname);

app.use(express.static(__dirname + '/www/'));

app.get('/', function (req, res) {
res.sendFile(__dirname + '/www/home.html');
});

paypal.configure({
'mode': 'sandbox', //sandbox or live
'client_id': 'XXXXX',
'client_secret': 'XXXXX'
});

app.post('/makePayment', (req, res) => {
var create_payment_json = {
"intent": "sale",
"payer": {
"payment_method": "paypal"
},
"redirect_urls": {
"return_url": "http://192.168.125.3:3000/home.html",
"cancel_url": "http://192.168.125.3:3000/cancel.html"
},
"transactions": [{
"item_list": {
"items": [{
"name": "item",
"sku": "item",
"price": "1.00",
"currency": "USD",
"quantity": 1
}]
},
"amount": {
"currency": "USD",
"total": "1.00"
},
"description": "This is the payment description."
}]
};
console.log(create_payment_json);
paypal.payment.create(create_payment_json, function (error, payment) {
if (error) {
console.log('error', error);
// throw error;
} else {
console.log("Create Payment Response");
for (let i = 0; i < payment.links.length; i++) {
if (payment.links[i].method = 'REDIRECT') {
res.redirect(payment.links[i].href);
break;
}
}
console.log(payment);
}
});
})
const port = 3000;
app.listen(port);
console.log('Server started listening on port 3000');
`

Please let me know where I am wrong and how can I resolve it.