If input value is blank, assign a value of “empty”

问题:

So I have an input field, if it's blank, I want its value to be the words "empty", but if there is any value inputted, I want the value to be the inputted value. I want to use javascript for this, any idea how this can be done?

UPDATE: Sorry, I don't think I explained it too well. I don't mean placeholder text. I mean the captured value of it. So if it's blank, the captured val() for it should be "empty", if it's filled, the captured val() for it should be that val()

回答1:

If you're using pure JS you can simply do it like:

var input = document.getElementById('myInput');

if(input.value.length == 0)
    input.value = "Empty";

Here's a demo: http://jsfiddle.net/nYtm8/

回答2:

I'm guessing this is what you want...

When the form is submitted, check if the value is empty and if so, send a value = empty.

If so, you could do the following with jQuery.

$('form').submit(function(){
    var input = $('#test').val();
    if(input == ''){
         $('#test').val('empty');
    }    
});

HTML

<form> 
    <input id="test" type="text" />
</form>

http://jsfiddle.net/jasongennaro/NS6Ca/

Click your cursor in the box and then hit enter to see the form submit the value.

回答3:

You can set a callback function for the onSubmit event of the form and check the contents of each field. If it contains nothing you can then fill it with the string "empty":

<form name="my_form" action="validate.php" onsubmit="check()">
    <input type="text" name="text1" />
    <input type="submit" value="submit" />
</form>

and in your js:

function check() {
    if(document.forms["my_form"]["text1"].value == "")
        document.forms["my_form"]["text1"].value = "empty";
}

回答4:

This can be done using HTML5's placeHolder or using JavaScript. Checkout this post.

回答5:

You can do this:

var getValue  = function (input, defaultValue) {
    return input.value || defaultValue;
};

回答6:

I think the easiest way to solve this issue, if you only need it on 1 or 2 boxes is by using the HTML input's "onsubmit" function.

Check this out and i will explain what it does:

<input type="text" name="val" onsubmit="if(this == ''){$this.val('empty');}" />

So we have created the HTML text box, assigned it a name ("val" in this case) and then we added the onsubmit code, this code checks to see if the current input box is empty and if it is, then, upon form submit it will fill it with the words empty.

Please note, this code should also function perfectly when using the HTML "Placeholder" tag as the placeholder tag doesn't actually assign a value to the input box.