Как ограничить input html

Limit number of characters allowed in form input text field

How do I limit or restrict the user to only enter a maximum of five characters in the textbox? Below is the input field as part of my form:

14 Answers 14

The maximum number of characters that will be accepted as input. This can be greater that specified by SIZE , in which case the field will scroll appropriately. The default is unlimited.

However, this may or may not be affected by your handler. You may need to use or add another handler function to test for length, as well.

I found this answer useful when limiting in the inputting phase. You can also limit it in the validation phase when submitting and pop up a validation message using the pattern attribute. See stackoverflow.com/questions/10281962/…

The simplest way to do so:

So.. Adding this attribute to your control:

Add the following to the header:

this.form.sessionNo seems a little suspect. Why not just this ? Also, limitCount and limitNum also seem out of order/unnecessary?

Corrected it. Doing this way if you wanted to limit it to certain characters or numbers you could, but if you don’t care about that then max Length would work fine. So say if you wanted the values to be between 1-50 you could or all positive numbers, etc.

this.form.sessionNo still doesn’t seem right. this in that context will point to the input , not document .

Still not right, it doesn’t reference the form either. this is all you need. Also, technically if you were wanting to reference the element by the form , it would be by ( form / input ) name , not id , ie: document.formName.sessionNum .

Correct I typed to fast it was wrapped in the a form before. But you’d just pass the ref to the input into the function to get the current value of the field then add any logic you want to limit that field.

and use an alert to show that max chars have been used.

According to w3c, the default value for the MAXLENGTH attribute is an unlimited number. So if you don’t specify the max a user could cut and paste the bible a couple of times and stick it in your form.

Even if you do specify the MAXLENGTH to a reasonable number make sure you double check the length of the submitted data on the server before processing (using something like php or asp) as it’s quite easy to get around the basic MAXLENGTH restriction anyway

@lopezdp, there are multiple ways to «get around» html/javascript restrictions. The easiest to check is to open your page with Chrome, «inspect element» and manually modify HTML. The more elaborate way to get around — write a script that will post the data ignoring any restrictions (using curl library or something similar). As a backend developer you should never trust frontend validation of data — all the rules should be duplicated on server. Frontend validation is just a way to save time for the user by pointing at obvious errors without making a request to the server.

the maximum amount of letters that can be in the input is 5.

The maximum number of characters that will be accepted as input. The maxlength attribute specifies the maximum number of characters allowed in the element.

Источник

Атрибуты minlength и maxlength

Атрибуты minlength и maxlength устанавливают полям ввода минимальное и максимальное количество символов.

Время чтения: меньше 5 мин

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Кратко

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Атрибуты minlength и maxlength позволяют устанавливать минимальное и максимальное количество символов в полях ввода или .

Как пишется

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  input minlength="4" maxlength="8"> textarea minlength="50" maxlength="1000">    Скопировать Скопировано Не удалось скопировать   

 Введите пароль (от 8 до 16 символов):  type="password" name="password" required minlength="8" maxlength="16"> label for="password">Введите пароль (от 8 до 16 символов):label> input type="password" id="password" name="password" required minlength="8" maxlength="16" >    Скопировать Скопировано Не удалось скопировать