跟踪在输入字段中是否按了退格键或Delete键

Question

I was wondering how i can track if users hit the backspace or delete key in a input field. Afterwhich i would add to a variable called count each time those buttons are pressed. I currently have this code but it does not seem to work; any help is great appreciated, thank you.

var Count = 0;

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

input.onkeydown = function() {
    var key = event.keyCode || event.charCode;

    if( key == 8 || key == 46 )
        Count++;
        return false;
};

Answer 1

multiple lines inside a conditional or loop, etc. need to be wrapped in braces:

if( key == 8 || key == 46 )
{
    Count++;
    return false;
}

You will also want to add a default return true as the last line to differentiate whether you entered the if or not as well.

Answer 2

Try this approach:

var count = 0;

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

input.onkeydown = function() {
    var key = event.keyCode || event.charCode;

    if( key !== 8 && key !== 46 )
        return true;

    count++;
};

1. Don't start your variable names with a capital letters unless they are object prototypes you're going to instantiate, ie. var count = new Count( ) , where you previously defined the Count object prototype

2. Always use a strict comparator, like === and !== , don't just use == and !=

3. Check for negative first, and return true if your condition doesn't match. Then execute your code, in your case count++