Strings in JS
Tags: javascript, programming, codenewbie, strings
Published: 2022-03-05 20:42:17

The string object is used to represent and manipulate the character.

**Note**: that JavaScript distinguishes between **String objects** and primitive **String values**.

---

1. **String literals** (denoted by _double_ ("Moreshwar") or _single_ ('Moreshwar') quotes).


2. Strings returned from String calls in a **non-constructor context** (that is, called without using the **new keyword**) are **primitive** strings. 


3. JavaScript **automatically converts primitives to String objects**, so that it's possible to use String object methods for primitive strings. 


4. In contexts where a method is to be invoked on a primitive string or a property lookup occurs, **JavaScript will automatically wrap the string primitive and call the method or perform the property lookup.property lookup**.


Some of the useful methods for strings are as follow.

**1. string.length()**

```
const firstName = "Moreshwar";

console.log(firstName.length); // o/p: 9

console.log("Moreshwar".length); // o/p: 9
```

- Behind the sceen the method is been call'ed (i.e _**PREMITIVE**_ Strings).

- JS will automatically convert existing **String** to **String Object** with same content.

- Hence, above example would be like **new String("Moreshwar")**.

**2. string.slice(BeginParamater,EndParameter)**

console.log(airline.slice(2, 5));


- Creates substring, if we do not specify the ENDSTRING everything will be extracted.


```
console.log(firstName.slice(2, 5)); // o/p: res 
```

```
console.log("123456789".slice(-4)); // o/p: 6789
```

**3. string.split("parameter")**

- The `split() `method divides a String into an ordered list of substrings, puts these substrings into an array, and returns the array.

For Ex.  

```
console.log("Moreshwar".split());
console.log("CODE + DAILY".split("+")); // ['CODE','DAILY']
```

**4. string.join("parameter")**

- The `join()` method creates and returns a new string by concatenating all of the elements in an array (or an array-like object), separated by commas or a specified separator string.

For Ex.  

```
let name = ["Mr.".toUpperCase(), "Moreshwar" ,"Pidadi"];
console.log(name.join()); // MR. Moreshwar Pidadi 
```


**5. string.padStart(targetLength, padString)**

- The `padStart() `method pads the current string with another string (multiple times, if needed) until the resulting string reaches the given length. The padding is applied from the start of the current string.

- The `padEnd()` method pads the current string with a given string (repeated, if needed) so that the resulting string reaches a given length. The padding is applied from the end of the current string.


```
const message = "Hello every one this is string 
method padStart() and padEnd()";
console.log(message.padStart(0, "*"));
console.log(message.padStart(50, "*").padEnd(35, "#"));

o/p:

****Hello every one this is string method padStart() and padEnd()
***Hello every one this is string method padStart() and padEnd()######
```


**6. string.repeat(number)**

- The `repeat()` method constructs and returns a new string which contains the specified number of copies of the string on which it was called, concatenated together.


```
console.log("Moreshwar".repeat(5));

o/p: 
     Moreshwar
     Moreshwar
     Moreshwar
     Moreshwar
     Moreshwar
```