What is the best way to change the first letter of a string to uppercase in JavaScript?

Creating a form with 10 textboxes and one button, I want the first letter of any text entered into a textbox to be capitalized when the user loses focus on that specific field. To achieve this functionality, JavaScript seems like the most suitable option. By utilizing the onblur event for all 10 textboxes, we can ensure that the desired behavior is implemented without relying on the onclick event of the button.

// JavaScript Function

function capitalizeFirstLetter(string)
{
    return string.charAt(0).toUpperCase() + string.slice(1);
}

// C# File 

page_load()
{
    string s1 = TextBox1.Text.Trim();
    TextBox1.Attributes.Add("Onblur",capitalizeFirstLetter('"+s1+"'))
}

While attempting to capitalize the first letter in pageload(), the variable s1 remains empty causing the function not to work as intended. What would be the best approach to address this issue?

javascriptasp.net

Answer №1

Follow these steps...

function onPageLoad()
{
    TextBox1.Attributes.Add("onblur", "makeFirstLetterUppercase('" + TextBox1.ClientID + "')");
}

Update your JavaScript function like so...

function makeFirstLetterUppercase(inputID) {
    var inputValue = document.getElementById(inputID).value;
    document.getElementById(inputID).value = inputValue.charAt(0).toUpperCase() + inputValue.slice(1);
}

Answer №2

To implement the onblur event in an aspx page, follow these steps.

<asp:TextBox ID="TextBox1" runat="server" onblur="capitalizeFirstLetter(this)">
</asp:TextBox>

The corresponding javaScript code is shown below.

<script language="javascript">
     function capitalizeFirstLetter(textBox)
     {
         return textBox.value.charAt(0).toUpperCase() + string.slice(1);
     } 
</script>

Answer №3

let firstLetter = str.charAt(0);
let restOfString = str.slice(1);
let capitalizedString = firstLetter.toUpperCase() + restOfString;
console.log(capitalizedString);

Answer №4

This is a straightforward solution involving variables in just two lines.

Only the first letter of a string will be capitalized, while the rest will remain lowercase.

let phrase = "series of terms"
let capitalizedPhrase = (phrase.slice(0,1)).toUpperCase() + (phrase.slice(1)).toLowerCase();

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