How to process each letter of text using JavaScript ?

Given a string and the task is to process it character by character.

  • JavaScript String toUpperCase() Method: This method converts a string to uppercase letters.
    Syntax:

    string.toUpperCase()
    

    Parameters: This method accepts single parameter str which is required. It specifies the string to be searched.

    Return Value: It returns a string denoting the value of a string converted to uppercase.

  • JavaScript String charAt() Method: This method returns the character at the passed index in a string. The index of characters strarts from 0.

    Syntax:

    string.charAt(index)
    

    Parameters: This method accepts single parameter index which is required. It specifies the integer representing the index of the character to return.

    Return Value: It returns a string, denoting the character at the passed index, or an empty string if the index number is invalid.

Example 1: This example processes the string letter by letter using for loop and converts each letter to uppercase separately.

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<!DOCTYPE HTML> 
<html
    <head
        <title
            How to process each character of text
        </title>
    </head
      
    <body style = "text-align:center;"
      
        <h1 style = "color:green;"
            GeeksForGeeks 
        </h1>
      
        <p id = "GFG_UP" style
            "font-size: 15px; font-weight: bold;">
        </p>
          
        <button onclick = "gfg_Run()"
            check
        </button>
          
        <p id = "GFG_DOWN" style
            "color:green; font-size: 20px; font-weight: bold;">
        </p>
          
        <script>
            var el_up = document.getElementById("GFG_UP");
            var el_down = document.getElementById("GFG_DOWN");
            var str = "This is String";
            el_up.innerHTML = "String = '"+str + "'";
          
            function gfg_Run() {
                var str_Upper = "";
                for (var i = 0; i < str.length; i++) {
                    str_Upper += str.charAt(i).toUpperCase();
                }
                el_down.innerHTML = str_Upper;
            }         
        </script> 
    </body
</html>                    

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Output:

  • Before clicking on the button:
  • After clicking on the button:

Example 2: This example processes the string letter by letter using for in loop and alerts each letter separately.

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<!DOCTYPE HTML> 
<html
    <head
        <title
            How to process each letter of text
        </title>
    </head
      
    <body style = "text-align:center;"
      
        <h1 style = "color:green;"
            GeeksForGeeks 
        </h1>
      
        <p id = "GFG_UP" style
            "font-size: 15px; font-weight: bold;">
        </p>
          
        <button onclick = "gfg_Run()"
            check
        </button>
          
        <script>
            var el_up = document.getElementById("GFG_UP");
            var str = "str";
            el_up.innerHTML = "String = '" + str + "'";
          
            function gfg_Run() {
                for (var i in str) {
                    alert(" character = "+str.charAt(i));
                }
            }         
        </script
    </body
</html>                    

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Output:

  • Before clicking on the button:
  • After clicking on the button:




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