How to restrict number of characters that can be e

问题:

It seems that neither of the "maxlength", "min" or "max" HTML attributes have the desired effect on iPhone for the following markup:

 <input type="number" maxlength="2" min="0" max="99"/>

Instead of limiting the number of digits or the value of the number entered, the number is just left as it was typed in on iPhone 4. This markup works on most other phones we tested.

What gives?

Any workarounds?

If it is important to the solution, we use jQuery mobile.

Thanks!

回答1:

Example

JS

function limit(element)
{
    var max_chars = 2;

    if(element.value.length > max_chars) {
        element.value = element.value.substr(0, max_chars);
    }
}

HTML

<input type="number" onkeydown="limit(this);" onkeyup="limit(this);">

If you are using jQuery you can tidy up the JavaScript a little:

JS

var max_chars = 2;

$('#input').keydown( function(e){
    if ($(this).val().length >= max_chars) { 
        $(this).val($(this).val().substr(0, max_chars));
    }
});

$('#input').keyup( function(e){
    if ($(this).val().length >= max_chars) { 
        $(this).val($(this).val().substr(0, max_chars));
    }
});

HTML

<input type="number" id="input">

回答2:

According to MDN, maxlength is not used for numbers. Have you tried just:

<input type="number" min="0" max="99" />

OR

<input type="range" min="0" max="99" />

回答3:

Check this out, it works for me;

Is there a minlength validation attribute in HTML5?

回答4:

as Andrew said you need to change the type to range, beside that you are going to have problems with IE and FF and probably old ipad browser because that's from HTML 5, and it's a "Kind New". Take a look to this person who tried the range with JS, Specify range of numbers to input in number field using javascript

回答5:

You can use JavaScript to check how many characters are in the box and if there are too many, remove one: http://www.webcodingtech.com/javascript/limit-input-text.php

回答6:

Here a more optimized jQuery version that caches the selectors. It also uses the maxlength attribute that is not supported by input type number.

// limits the input based on the maxlength attribute, this is by default no supported by input type number
$("input[type=number]").on('keydown keyup',function(){ 
    var $that = $(this),
    maxlength = $that.attr('maxlength')
    if($.isNumeric(maxlength)){
        $that.val($that.val().substr(0, maxlength));
    };
});

回答7:

Another option with jQuery, but onkeypress event... ;)

$("input[type=number]").on('keypress',function(e) { 
    var $that = $(this),
    maxlength = $that.attr('maxlength')
    if($.isNumeric(maxlength)){
        if($that.val().length == maxlength) { e.preventDefault(); return; }

        $that.val($that.val().substr(0, maxlength));
    };
});

回答8:

you can use this code:

<input type="number" maxlength="2" min="0" max="99"
       onkeypress="limitKeypress(event,this.value,2)"/>

and js code:

function limitKeypress(event, value, maxLength) {
    if (value != undefined && value.toString().length >= maxLength) {
        event.preventDefault();
    }
}

回答9:

I know this question is one year old, but I don't prefer the selected answer. Because the way it works is that it shows the character that is typed and then removes it.

In contrast I will propose another way which is similar to Will's, it is just better in the way that it prevents the character from being shown. Also I've added an else if block to check if the character is a number and then it is a good function to validate the number fields.

HTML

<input type="number" onkeydown="limit(this);">

JS

function limit(element)
{
    var max_chars = 2;
    if (arguments[1].char !== "\b" && arguments[1].key !== "Left" && arguments[1].key !== "Right") {
        if (element.value.length >= max_chars) {
            return false;
        } else if (isNaN(arguments[1].char)) {
            return false;
        }
    }
}

回答10:

This is Tripex answer optimized for allowing delete key, works when typing and on paste.

$(document).on("keyup", "#your_element", function(e) {
    var $that = $(this),
    maxlength = $that.attr('maxlength');
    if ($.isNumeric(maxlength)){
        if($that.val().length === maxlength) {
            e.preventDefault();
            // If keyCode is not delete key 
            if (e.keyCode !== 64) {
                return;
            }
        }
        $that.val($that.val().substr(0, maxlength));
    }
});