Basics Of Javascript
Tags: web, javascript
Published: 2024-05-10 14:08:32

**Javascript :** JavaScript is a lightweight, cross-platform, single-threaded, and interpreted compiled programming language. It is also known as the scripting language for webpages. It is well-known for the development of web pages, and many non-browser environments also use it.

## Some Basic Concepts

- <u>String</u>
```

`Run each function to see the output, play and learn by doing

// Length
function getLength(str) {
  console.log("Original String:", str);
  console.log("Length:", str.length);
}
getLength("Hello World");

// indexOf
function findIndexOf(str, target) {
  console.log("Original String:", str);
  console.log("Index:", str.indexOf(target));
}
findIndexOf("Hello World", "World");

// lastIndexOf
function findLastIndexOf(str, target) {
  console.log("Original String:", str);
  console.log("Index:", str.lastIndexOf(target));
}
findLastIndexOf("Hello World World", "World");

// slice
function getSlice(str, start, end) {
  console.log("Original String:", str);
  console.log("After slice:", str.slice(start, end));
}
getSlice("HelloWorld", 2, 5);
getSlice("HelloWorld", -5, -2);
// substring
function getSubstring(str, start, end) {
  console.log("Original String:", str);
  console.log("After substring:", str.substring(start, end));
}
getSubstring("Hello World", 1, 5);
getSubstring("Hello World", -5, -1);

// replace
function replaceString(str, target, replacement) {
  console.log("Original String:", str);
  console.log("After replace:", str.replace(target, replacement));
}
replaceString("Hello World", "World", "JavaScript");

// split
function splitString(str, separator) {
  console.log("Original String:", str);
  console.log("After split:", str.split(separator));
}
splitString("Hello World", " ");

// trim
function trimString(str) {
  console.log("Original String:", str);
  console.log("After trim:", str.trim());
}
trimString(" Hello   World ");

// toUpperCase
function toUpper(str) {
  console.log("Original String:", str);
  console.log("After toUpperCase:", str.toUpperCase());
}
toUpper("Hello World");

// toLowerCase
function toLower(str) {
  console.log("Original String:", str);
  console.log("After toLowerCase:", str.toLowerCase());
}
toLower("Hello World");
`
```

- <u>Number</u>
```
function explainParseInt(value) {
  console.log("Original Value:", value);
  let result = parseInt(value);
  console.log("After parseInt:", result);
}

// Example Usage for parseInt
explainParseInt("42");
explainParseInt("42px");
explainParseInt("3.14");

function explainParseFloat(value) {
  console.log("Original Value:", value);
  let result = parseFloat(value);
  console.log("After parseFloat:", result);
}

// Example Usage for parseFloat
explainParseFloat("3.14");
explainParseFloat("42");
explainParseFloat("42px");

```

- <u>Array</u>

```
function explainParseInt(value) {
  console.log("Original Value:", value);
  let result = parseInt(value);
  console.log("After parseInt:", result);
}

// Example Usage for parseInt
explainParseInt("42");
explainParseInt("42px");
explainParseInt("3.14");

function explainParseFloat(value) {
  console.log("Original Value:", value);
  let result = parseFloat(value);
  console.log("After parseFloat:", result);
}

// Example Usage for parseFloat
explainParseFloat("3.14");
explainParseFloat("42");
explainParseFloat("42px");

```

- <u>Class</u>

```

class Animal {
  constructor(name, legCount) {
    this.name = name
    this.legCount = legCount
  }
  describe() {
    return `${this.name} has ${this.legCount} legs`
  }
}

let O1=new Animal("dog",4);
let detail=O1.describe();
console.log(detail);

```

- <u>Date</u>

```
function dateMethods() {
  const currentDate = new Date();
  console.log("Current Date:", currentDate);

  // Getting various components of the date
  console.log("Date:", currentDate.getDate());
  console.log("Month:", currentDate.getMonth() + 1); // Months are zero-indexed, so adding 1
  console.log("Year:", currentDate.getFullYear());
  console.log("Hours:", currentDate.getHours());
  console.log("Minutes:", currentDate.getMinutes());
  console.log("Seconds:", currentDate.getSeconds());

  // Setting components of the date
  currentDate.setFullYear(2022);
  console.log("After setFullYear:", currentDate);

  currentDate.setMonth(5); // Setting month to June (zero-indexed)
  console.log("After setMonth:", currentDate);

  // Getting and setting time in milliseconds since 1970
  console.log("Time in milliseconds since 1970:", currentDate.getTime());

  const newDate = new Date(2023, 8, 15); // Creating a new date
  console.log("New Date:", newDate);
}

// Example Usage for Date Methods
dateMethods();

```

- <u>Json</u>

```
function jsonMethods(jsonString) {
  console.log("Original JSON String:", jsonString);

  // Parsing JSON string to JavaScript object
  let parsedObject = JSON.parse(jsonString);
  console.log("After JSON.parse():", parsedObject);

  // Stringifying JavaScript object to JSON string
  let jsonStringified = JSON.stringify(parsedObject);
  console.log("After JSON.stringify():", jsonStringified);
}

// Example Usage for JSON Methods
const sampleJSONString =
  '{"key": "value", "number": 42, "nested": {"nestedKey": "nestedValue"}}';

jsonMethods(sampleJSONString);

```

- **setInterval
 :** is a JavaScript function used to repeatedly execute a given function at fixed time intervals. It is commonly used for tasks that require periodic updates or actions on web pages, such as updating live data, creating animations, or implementing countdown timers.

---

**Syntax**
`setInterval(function, interval);
`

```

`// Example: Execute a function every 1 second
const intervalId = setInterval(myFunction, 1000);

function myFunction() {
    console.log("Executing function every 1 second");
}

// To stop the interval after a certain period, you can use clearInterval:
setTimeout(() => {
    clearInterval(intervalId);
    console.log("Interval stopped after 5 seconds.");
}, 5000);
`


```