DEV Community

loading...
Cover image for 😬15 Very Important Javascript String Methods Every Developer Should Know

😬15 Very Important Javascript String Methods Every Developer Should Know

satishnaikawadi2001 profile image Satish Naikawadi Originally published at satishnaikawadi.me ・5 min read

Manipulation of javascript strings are very important in most of the web development projects. So , in this post we will take a look 😍 at some important and frequently used string methods in javascript. Below are the strings which we will used to learn this methods with.

var stringOne = "Let's learn important javascript string methods."
var stringTwo = "Also we will see their examples."
Enter fullscreen mode Exit fullscreen mode

charAt()

The String object's charAt() method returns a new string consisting of the single UTF-16 code unit located at the specified offset into the string.If the index cannot be converted to the integer or no index is provided, the default is 0, so the first character of string is returned.

const index = 4;
console.log(`Character at index ${index} in stringOne is ${stringOne.charAt(index)}`);
Enter fullscreen mode Exit fullscreen mode

Output

Character at index 4 in stringOne is s

concat()

The concat() method concatenates the string arguments to the calling string and returns a new string. If the arguments are not of the type string, they are converted to string values before concatenating.

console.log(stringOne.concat(stringTwo));
console.log(stringOne.concat('And ', stringTwo));
Enter fullscreen mode Exit fullscreen mode

Output

Let's learn important javascript string methods.Also we will see their examples.
Let's learn important javascript string methods.And Also we will see their examples.

endsWith()

The endsWith() method determines whether a string ends with the characters of a specified string, returning true or false as appropriate. This method is case-sensitive. If second argument provided, it is used as the length of string. Defaults to string.length.

console.log(stringOne.endsWith('methods.'));
console.log(stringOne.endsWith('javascript'));
console.log(stringOne.endsWith('javascript', 32));
Enter fullscreen mode Exit fullscreen mode

Output

true
false
true

includes()

The includes() method performs a case-sensitive search to determine whether one string may be found within another string, returning true or false as appropriate. The second argument is position within the string at which to begin searching for searchString. (Defaults to 0.)

console.log(stringOne.includes("Let's"));
console.log(stringOne.includes("Let's", 1)); //Start searching from first index
console.log(stringOne.includes("let's")); //Case sensitive
Enter fullscreen mode Exit fullscreen mode

Output

true
false
false

indexOf()

The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. Returns -1 if the value is not found. fromIndex is the second argument which is an integer representing the index at which to start the search. Defaults to 0.

console.log(stringOne.indexOf('a'));
console.log(stringOne.indexOf('a', 15)); //Start searching from index 15
Enter fullscreen mode Exit fullscreen mode

Output

8
18

lastIndexOf()

The lastIndexOf() method is same as indexOf() method only difference is instead of first occurence it search for last occurence of a given string. It returns the index of the last occurrence of searchValue; -1 if not found.

console.log(stringOne.lastIndexOf('a'));
Enter fullscreen mode Exit fullscreen mode

Output

25

replace()

The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match. If pattern is a string, only the first occurrence will be replaced.
The original string is left unchanged.

console.log(stringOne.replace('methods', 'functions'));
console.log(stringOne.replace('important', 'must know'));
const regex = /Javascript/i;
console.log(stringOne.replace(regex, 'JS'));
Enter fullscreen mode Exit fullscreen mode

Output

Let's learn important javascript string functions.
Let's learn must know javascript string methods.
Let's learn important JS string methods.

replaceAll() is also a similar method only difference is instead of replacing first match it will replace every match in the string.

startsWith()

The startsWith() method determines whether a string begins with the characters of a specified string, returning true or false as appropriate.The second argument is position in this string at which to begin searching for searchString. Defaults to 0.

console.log(stringOne.startsWith("Let's"));
console.log(stringOne.startsWith("Let's", 5)); // Start searching from position at index 5
Enter fullscreen mode Exit fullscreen mode

Output

true\
false

slice()

The slice() method extracts a section of a string and returns it as a new string, without modifying the original string. Its first argument is beginIndex - the zero-based index at which to begin extraction. And second srgument is endIndex - the zero-based index before which to end extraction. The character at endIndex will not be included.\
If any or both of the two endIndex and beginIndex are negative, then they are treated as str.length + endIndex and str.length + beginIndex . (For example, if endIndex is -3, it is treated as str.length - 3.)

console.log(`Length of stringOne is ${stringOne.length}`);
console.log(stringOne.slice(6, 22)); // Start at index 6 and extract upto index 22 not including 22
console.log(stringOne.slice(6, -9)); // Start at index 6 and extract upto index 48 - 9 = 39 not including 39
console.log(stringOne.slice(6)); // Start at index 6 and extract whole string
console.log(stringOne.slice(50)); // As startIndex is greater than length return empty string
Enter fullscreen mode Exit fullscreen mode

Output

Length of stringOne is 48
learn important
learn important javascript string
learn important javascript string methods.

split()

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

console.log(stringOne.split(' '));
console.log(stringOne.split('learn'));
Enter fullscreen mode Exit fullscreen mode

Output

[ "Let's", 'learn', 'important', 'javascript', 'string', 'methods.' ]
[ "Let's ", ' important javascript string methods.' ]

substr()

The substr() method returns a portion of the string, starting at the specified index and extending for a given number of characters afterwards.

console.log(stringOne.substr(6)); // Start at index 6 and extract whole remaining string
console.log(stringOne.substr(6, 34)); // Start at index 6 and extract next 34 characters.
Enter fullscreen mode Exit fullscreen mode

Output

learn important javascript string methods.
learn important javascript string

trim()

The trim() method removes whitespace from both ends of a string. Whitespace in this context is all the whitespace characters (space, tab, no-break space, etc.) and all the line terminator characters (LF, CR, etc.).

var stringThree = '       remove whitespaces       ';
console.log(stringThree.trim());
Enter fullscreen mode Exit fullscreen mode

Output

remove whitespaces

The trimEnd() and trimStart() are similar methods which removes whitespace from the end and start of the string respectively.

match()

The match() method retrieves the result of matching a string against a regular expression. You can learn about regular expression here .

const regex = /[A-Z]/g; // regex for capital characters
console.log(stringOne.match(regex));
Enter fullscreen mode Exit fullscreen mode

Output

[ 'L' ]

toLowerCase()

The toLowerCase() method returns the calling string value converted to lower case.

var stringThree = 'THIS IS DEMO STRING';
console.log(stringThree.toLowerCase());
Enter fullscreen mode Exit fullscreen mode

Output

this is demo string

toUpperCase()

The toUpperCase() method returns the calling string value converted to upper case.

var stringThree = 'this is demo string';
console.log(stringThree.totoUpperCase()());
Enter fullscreen mode Exit fullscreen mode

Output

THIS IS DEMO STRING

And that is it for this article. You can visit satishnaikawadi.me for more articles related to programming.Thanks for reading 😇 .

Discussion (3)

pic
Editor guide
Collapse
leviathanprogramming profile image
𝐋𝐄𝑽𝐈𝑨𝐓𝐇𝐀𝐍 Programming

Maybe you should add the replaceAll() function. It comes in handy lots of times.

Collapse
satishnaikawadi2001 profile image
Satish Naikawadi Author

Yes I have mentioned it in short below replace.

Collapse
vent2 profile image
Gerald Ventura

Thank you for this it was very informative. Also, I am new to this site and don't know if you can edit your post but you misspelled the second argument in slice().