How to check an undefined value?

In JavaScript we have different type of undefined values:

 if (this.state.subject.id === undefined) {
     console.log('this.state.subject.id: is undefined');
 }
 if (this.state.subject.id === null)  {
     console.log('this.state.subject.id: is null');
 }
 if (this.state.subject.id === "") {
     console.log('this.state.subject.id: is empty');
 }

Converting data type

From String to Integer

From String (with thousands separator) to Integer

var category = "8'100'000"
var categoryAsInteger = parseInt(category.replace(/'/g,""), 10);

Date and time operations

Get date time in YYYY-MM-dd hh:mm:SS format

var today = new Date();

var date = today.getFullYear().toString().substring(0) + '-' + (today.getMonth() + 1) + '-' + today.getDate();
var time = today.getHours() + ":" + today.getMinutes() + ":" + today.getSeconds();
var timeStamp = date + ' ' + time;
console.log(`timeStamp: ${timeStamp}`)

JSON operations

Logging of JSON Data

The following examples show different ways to log a JSON object:

let jsonObject = '{"name":"Mike Dane","login":"mdane","password":"12345"}';

console.log(`JSON: ${jsonObject}`);
console.log(`JSON.stringify(): ${JSON.stringify(jsonObject)}`);
console.log(`JSON.parse(): ${JSON.parse(jsonObject).name}`);

Logs:

JSON: {"name":"Mike Dane","login":"mdane","password":"12345"}
JSON.stringify(): "{\"name\":\"Mike Dane\",\"login\":\"mdane\",\"password\":\"12345\"}"
JSON.parse(): Mike Dane