---
---

#### index.js
```javascript
typeof my_variable;
// 'string'
// 'number'
// 'boolean'
// 'object' (array is object too)
// 'undefined'

isNaN(my_variable);

// Run a code 1 time after some time
setTimeout(() => {
    console.log('Hello');
}, 1000);

// Repeat a code on fixed interval
setInterval(() => {
    console.log('Hello');
}, 1000);
```

---
---

#### index.js
```javascript
document.getElementById('foo')
document.getElementsByClassName('foo')
document.getElementsByName('foo')
document.getElementsByTagName('foo')

typeof my_variable;
// 'string'
// 'number'
// 'boolean'
// 'object' (array is object too)
// 'undefined'

isNaN(my_variable);

// Run a code 1 time after some time
setTimeout(() => {
    console.log('Hello');
}, 1000);

// Repeat a code on fixed interval
setInterval(() => {
    console.log('Hello');
}, 1000);
```

Add note for getting element(s) in javascript
Add note for getting element(s) in javascript
