检查何时输入类型文本被填充

Question

I have a form with input types text. Like this:

<input type="text" placeholder="Voornaam" class="required" title="Voornaam" id="ctl00_ContentPlaceHolder1_tbFirstName" maxlength="255" value="Mike" name="ctl00$ContentPlaceHolder1$tbFirstName">

But now my question. Normally the text is gray in the text fields. But when you have completed a field. The color must be black. How can i check this with javascript?

Thanks

Answer 1

I think you meant that we need color field only when user finished writing.... If yes then you need to use this algorithm:

$('#ctl00_ContentPlaceHolder1_tbFirstName').blur(function () {
    var self = $(this);
    if (self.val() != "") {
        self.css('color','black'); // Set black fore color
    }
    else {
        self.css('color','gray'); // Restore code
    }
});

Answer 2

You could use the .change function in jquery to change the color to black when user type something and cursor moves out of the text field.

Ex:

$("input[type='text']").change(function(){

    $(this).css('color', 'black');
});

Answer 3

<input type="text" onblur="changeColor()" placeholder="Voornaam" 
 class="required" title="Voornaam" id="ctl00_ContentPlaceHolder1_tbFirstName" 
 maxlength="255" value="Mike" name="ctl00$ContentPlaceHolder1$tbFirstName">

define your changeColor() function, which will change color of text in the textbox.

Answer 4

The change event get triggered if you leave the input field (on blur). If you would like to have instant check use keyup event:

$('#ctl00_ContentPlaceHolder1_tbFirstName').bind('keyup', function(){
  if (someconditionistrue) $(this).css('color','black');
});

using the ID selector is faster than the attribute selector

Answer 5

This will apply this rule to all elements with the required class.

$('.required').blur(function () {
    if ($(this).val().trim().length == 0) 
        $(this).css('color','black');
    else 
        $(this).css('color','gray');
  });