How to use Javascript to lock a keyboard key and display alert in the field about the recommended key?

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4

How do I make a Javascript to block comma usage , within the field and at the same time also make an informed notification that point only . is allowed and also check if what the user has typed is correct.

I don’t have much knowledge in Javascript and I didn’t think much about it, the most I could find was onKeyCode and there was another that I forgot but got nothing.

Example: current weight: 70.80

javascript

2 answers

7


You can link an event in the input

Example:

document.querySelector('input').addEventListener('keypress', function(evt) {
    if (evt.key == ',') {
        evt.preventDefault()
        alert('Tecla inválida');
    }
});
<input type="text">

document.querySelector('input') will return you the element you want to link

addEventListener links a callback for a given event, in the example the linked event is keypress

function(evt){ console.log(evt.key); } is the callback, the action that will be executed when the event occurs.

You can call the method preventDefault() to prevent the standard event action

  • 1

    Maybe add evt.preventDefault() within the if to block, in fact, the use of the comma?

  • @Andersoncarloswoss, edited, had forgotten this detail :)

1

Have a jQuery event that is called keypress, by parameter you pass a function with an if if the comma key has been pressed ie :

Ex:

$(document).keypress(function(e) {
    if(e.which == 188) {
        alert('You pressed a virgula!');
    }
});

188 is the , of the keyboard. this site has the value of all: http://www.javascripter.net/faq/keycodes.htm

See if you can implement if you can’t answer me here

  • 1

    There is a very nice site, where you press the key and it shows the corresponding code, see keycode.info

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