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Strings in JavaScript

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In this video we will discuss different functions that are available to manipulate strings in JavaScript.

A string is any text inside quotes. You can use either single or double quotes.
var string1 = "string in double quotes"
var string2 = 'string in single quotes'

Concatenating strings : There are 2 options to concatenate strings in JavaScript. You could either use + operator or concat() method

Example : Concatenating strings using + operator
var string1 = "Hello"
var string2 = "JavaScript"
var result = string1 + " " + string2;

Output : Hello JavaScript

Example : Concatenating strings using concat() method
var string1 = "Hello"
var string2 = "JavaScript"
var result = string1.concat(" ", string2);

Output : Hello JavaScript

If you want single quotes inside a string, there are 2 options
Option 1 : Place your entire string in double quotes, and use single quotes inside the string wherever you need them.

Example : 
var myString = "Welcome to 'JavaScript' Training";

Output : Welcome to 'JavaScript' Training

Option 2 : If you prefer to place your entire string in single quotes, then use escape sequence character \ with a single quote inside the string.

Example : 
var myString = 'Welcome to \'JavaScript\' Training';

Output : Welcome to 'JavaScript' Training

Please Note : You can use the above 2 ways if you need double quotes inside a string

Converting a string to uppercase : Use toUpperCase() method

Example :
var upperCaseString = "JavaScript";


Converting a string to lowercase : Use toLowerCase() method

Example :
var lowerCaseString = "JavaScript";

Output : javascript

Length of string javascript : Use length property

Example : alert("JavaScript".length);

Output : 10

Example :
var myString = "Hello JavaScript";

Output : 16

Remove whitespace from both ends of a string : Use trim() method

Example :
var string1 = " AB ";
var string2 = " CD ";
var result = string1.trim() + string2.trim();

Output : ABCD

Replacing strings in javascript : Use replace() method. This method searches a given string for a specified value or a regular expression, replaces the specified values with the replacement values and returns a new string. This method does not change the original string.

Example : Replaces JavaScript with World
var myString = "Hello JavaScript";
var result = myString.replace("JavaScript", "World");

Output : Hello World

Example : Perform a case-sensitive global replacement. In this example, we are using a regular expression between the 2 forward slashes(//). The letter g after the forward slash specifies a global replacement. The match here is case sensitive. This means Blue(with capital B) is not replaced with green.

var myString = "A Blue bottle with a blue liquid is on a blue table";
var result = myString.replace(/blue/g, "green");

Output : A Blue bottle with a green liquid is on a green table

Example : Perform a case-insensitive global replacement. The letters gi after the forward slash indicates to do global case-insensitive replacement. Notice that the word Blue(with capital B) is also replaced with green.

var myString = "A Blue bottle with a blue liquid is on a blue table";
var result = myString.replace(/blue/gi, "green");

Output : A green bottle with a green liquid is on a green table

JavaScript tutorial


  1. Venkat,

    Could you please help me in this replace scenario?
    In this tutorial you said we can replace a word with /blue/g. In case of dynamic http tag, how could we replace a url string with desired word? for example I have a string that starts with https://...... . This entire url string I want to replace with say Hello world. How can I extract the entire url string starting from https:// and end with unknown as it is dynamic.

    The url could be or or could be any other unknown text.

    1. For special characters which has special meaning in javascript like single quote ,double quote and forward slash(/).if you want to treat them as regular printable characters then we can make use of the escape sequences(\).

      you can handle the forward slash / with the help of backslash \.use the back slash before the forward slash to treat it as string
      for example
      var url ="This is google Url and yahoo URL"

      We have above string and we want to replace the http:// with Hello.

  2. var myString = "A Blue bottle with a blue liquid is on a blue table";
    var name='blue';
    var result = myString.replace(/'name'/g, "green");

  3. Hi Venkat,

    In recent interview i have faced one question which i could not answer. The questions is what is the difference between below two lines of code.

    var name = "Kud Venkat";
    var anothername = new String("Kud Venkat");

    Can you please explain me, what is the difference between them. Thanks in advance.


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