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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;
alert(result);

Output : Hello JavaScript

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

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";
alert(myString);

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';
alert(myString);

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";
alert(upperCaseString.toUpperCase());

Output : JAVASCRIPT

Converting a string to lowercase : Use toLowerCase() method

Example :
var lowerCaseString = "JavaScript";
alert(lowerCaseString.toLowerCase());

Output : javascript

Length of string javascript : Use length property

Example : alert("JavaScript".length);

Output : 10

Example :
var myString = "Hello JavaScript";
alert(myString.length);

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();
alert(result);

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");
alert(result);

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");
alert(result);

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");
alert(result);

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

JavaScript tutorial

2 comments:

  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 http://www.google.com or http://www.pragim.com or could be any other unknown text.

    ReplyDelete
    Replies
    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 http://www.google.com and yahoo URL http://www.yahoo.com"

      We have above string and we want to replace the http:// with Hello.
      document.write(url.replace(/http:\/\//gi,"Hello"))

      Delete

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