13 Most Common JavaScript String Methods You Should Know About
Tags: webdev, javascript, programming, beginners
Published: 2023-11-18 06:30:26

In JavaScript, strings are sequences of characters. JavaScript provides a rich set of methods to manipulate and work with strings. In this post, I’ll introduce you to the 13 most commonly used JavaScript string methods and their functionalities.

## String length

If you want to find the number of characters in a string, then you can use the `length` property.

```js
const str = "This is a string.";
const lengthOfStr = str.length;
console.log(lengthOfStr); // Output: 17
```

This also counts white spaces.

## String toUpperCase()

If you want to convert a string to uppercase, then you can use the `toUpperCase()` method.

```js
const str = "This is a string.";
const uppercaseStr = str.toUpperCase();
console.log(uppercaseStr); // Output: THIS IS A STRING.
```

## String toLowerCase()

If you want to convert a string to lowercase, then you can use the `toLowerCase()` method.

```js
const str = "This Is a String.";
const lowercaseStr = str.toLowerCase();
console.log(lowercaseStr); // Output: this is a string.
```

## String indexOf()

If you want to find the first occurrence of a substring in a string then you can use the `indexOf()` method.

```js
const str = "This is a js string and js string is nice.";
const indexOfJs = str.indexOf("js");
console.log(indexOfJs); // Output: 10
```

## String lastIndexOf()

If you want to find the last occurrence of a substring in a string then you can use the `lastIndexOf()` method.

```js
const str = "This is a js string and js string is nice.";
const lastIndexOfJs = str.lastIndexOf("js");
console.log(lastIndexOfJs); // Output: 24
```

## String slice()

If you want to extract a part of a string, then you can use the `slice()` method. This will return the extracted part in a new string.

Syntax:

```
string.slice(start position, end position);
```
The end position will not be included.

```js
//Example:1
const str1 = "This is a string.";
const slicedStr1 = str1.slice(0, 7);
console.log(slicedStr1); // Output: This is

//Example:2
const str2 = "This is a string.";
const slicedStr2 = str2.slice(3, 9);
console.log(slicedStr2); // Output: s is a
```

If you don’t specify the end position then this will slice out the rest of the string.
For example:

```js
const str = "This is a string.";
const slicedStr = str.slice(5);
console.log(slicedStr); // Output: is a string.
```

You can also give it negative parameters.

For example:

```js
const str = "This is a string.";
const slicedStr = str.slice(-3, -1);
console.log(slicedStr); // Output: ng
```
To put it simply, you can understand this as:

```js
str.slice(-3, -1);
str.slice(str.length-3, str.length-1);
str.slice(17-3, 17-1);
str.slice(14, 16);
```

## String substring()

The `substring()` method is similar to the `slice()` method, but the difference is that if you give it negative parameters (less than 0) then they will be treated as 0.

```js
const str = "This is a string.";
const slicedStr = str.substring(-3, 5);
console.log(slicedStr); // Output: This
```

## String substr()

The `substr()` method is similar to the `slice()` method, but the difference is that the end parameter is the length of the characters to be extracted.

```js
const str = "This is a string.";
//This will extract the characters staring from index 11 
//and will extract 4 characters.
const slicedStr = str.substr(11, 4); 
console.log(slicedStr); // Output: trin
```

## String charAt()

If you want to get a character at a specified index in a string, then you can use the `charAt()` method.

```js
const str = "This is a string.";
const character = str.charAt(13);
console.log(character); // Output: i
```

## String concat()

If you want to concatenate two or more strings, then you can use the `concat()` method.

```js
const firstName = "John";
const lastName = "Doe";
const fullName = firstName.concat(" ", lastName);
console.log(fullName); // Output: John Doe
```

## String trim()

You can remove whitespace from both ends of a string using the `trim()` method.

```js
const str = "    This is a string.    ";
const trimmedStr = str.trim();
console.log(trimmedStr); // Output: This is a string.
```

## String replace()

If you want to replace a specified substring with another string, then you can use the `replace()` method.

```js
const str = "JavaScript is amazing!";
const replacedStr = str.replace("amazing", "awesome");
console.log(replacedStr); // Output: JavaScript is awesome!
```

## String split()

You can convert a string into an array using the `split()` method.

```js
const str1 = "JavaScript is amazing!";
const arr1 = str1.split();
console.log(arr1); // Output: ['JavaScript is amazing!']

//Example:2
const str2 = "JavaScript is amazing!";
const arr2 = str2.split(" ");
console.log(arr2); // Output: ['JavaScript', 'is', 'amazing!']
```
That’s all for today.

Thanks for reading.

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