How to Prevent a User from Entering Negative Values in HTML Input

Is there any way to prevent input type=number getting negative values?

Use the min attribute like this:

<input type="number" min="0">

How to prevent a user from entering negative values in Html input

Due to the <input type="number"> still not being widely well supported, you are still better off using a text input. Preventively you could disallow any characters which are not numbers with the keypress event and e.preventDefault(). However be sure that if you want to support legacy browsers (IE8-), there are a number of inconsistencies to take into account regarding returned key codes/ char codes. If you also want to disallow pasting non-number content, you can do so with the paste event and e.clipboardData.getData('plain/text') (for a complete implementation see here)

Test with the code below:

var myInput = document.getElementsByTagName('input')[0];myInput.addEventListener('keypress', function(e) {  var key = !isNaN(e.charCode) ? e.charCode : e.keyCode;  function keyAllowed() {    var keys = [8,9,13,16,17,18,19,20,27,46,48,49,50,                51,52,53,54,55,56,57,91,92,93];    if (key && keys.indexOf(key) === -1)      return false;    else      return true;  }  if (!keyAllowed())    e.preventDefault();}, false);
// EDIT: Disallow pasting non-number contentmyInput.addEventListener('paste', function(e) {  var pasteData = e.clipboardData.getData('text/plain');  if (pasteData.match(/[^0-9]/))    e.preventDefault();}, false);

<input type="text">

Prevent negative inputs in form input type=number?

This uses Javascript, but you don't have to write your own validation routine. Instead just check the validity.valid property. This will be true if and only if the input falls within the range.

<html><body><form action="#">  <input type="number" name="test" min=0 oninput="validity.valid||(value='');"><br>  <input type="submit" value="Submit"></form></body></html>

How to prevent a user from entering negative values in Html input

Test with the code below:

var myInput = document.getElementsByTagName('input')[0];myInput.addEventListener('keypress', function(e) {  var key = !isNaN(e.charCode) ? e.charCode : e.keyCode;  function keyAllowed() {    var keys = [8,9,13,16,17,18,19,20,27,46,48,49,50,                51,52,53,54,55,56,57,91,92,93];    if (key && keys.indexOf(key) === -1)      return false;    else      return true;  }  if (!keyAllowed())    e.preventDefault();}, false);
// EDIT: Disallow pasting non-number contentmyInput.addEventListener('paste', function(e) {  var pasteData = e.clipboardData.getData('text/plain');  if (pasteData.match(/[^0-9]/))    e.preventDefault();}, false);

<input type="text">

Preventing user from entering negative numbers in input elements with number type

You were only adding the event listeners to the first number input.

https://jsfiddle.net/tpsbnp9q/5/

var myInput = document.querySelectorAll("input[type=number]");

function keyAllowed(key) {
  var keys = [8, 9, 13, 16, 17, 18, 19, 20, 27, 46, 48, 49, 50,
    51, 52, 53, 54, 55, 56, 57, 91, 92, 93
  ];
  if (key && keys.indexOf(key) === -1)
    return false;
  else
    return true;
}

myInput.forEach(function(element) {
  element.addEventListener('keypress', function(e) {
    var key = !isNaN(e.charCode) ? e.charCode : e.keyCode;
    if (!keyAllowed(key))
      e.preventDefault();
  }, false);

  // Disable pasting of non-numbers
  element.addEventListener('paste', function(e) {
    var pasteData = e.clipboardData.getData('text/plain');
    if (pasteData.match(/[^0-9]/))
      e.preventDefault();
  }, false);
})

How to avoid negative numbers in html input?

You can use min property

<input type="number" min="0" name="amount" placeholder="0.001" step="0.001"  required>

How to prevent user from entering negative number in react?

Handling Empty Input & Negative Numbers

// Converting App into Class-Component
class App extends React.Component {
  // Set State
  constructor(props) {
    super(props);
    this.state = {
      number: ""
    };
  }

  render() {
    return (
      <div className="App">
        <input
          type="number"
          min="0"
          step="1"
          onChange={(e) => {
            let val = parseInt(e.target.value, 10);
            if (isNaN(val)) {
              this.setState({ number: "" });
            } else {
              // is A Number
              val = val >= 0 ? val : 0;
              this.setState({ number: val });
            }
          }}
          className="w-100"
          // Assign State
          value={this.state.number}
        />
      </div>
    );
  }
}

How to block negative values in Input tags while entering in forms

Our conditions are:

Positive Numbers
Integers only (non-decimals)

We should handle:

Mouse events
Keyboard events

For mouse events, we will cover it with input API as normal HTML element, by using min={0} and step={1}.

For keyboard events, the trick is to prevent press event on invalid input.

So we will try and rewrite this plain HTML as React DOM element:

<input type="number" onkeypress="return event.charCode >= 48" min="0" step="1" />

export default function App() {
  return (
    <input
      type="number"
      min={0}
      step={1}
      onKeyPress={(event) => {
        if (event.charCode < 48) {
          event.preventDefault();
        }
      }}
    />
  );
}

Edit adoring-swanson-j5k59

How to Prevent a User from Entering Negative Values in HTML Input

Is there any way to prevent input type=number getting negative values?

How to prevent a user from entering negative values in Html input

Prevent negative inputs in form input type=number?

How to prevent a user from entering negative values in Html input

Preventing user from entering negative numbers in input elements with number type

How to avoid negative numbers in html input?

How to prevent user from entering negative number in react?

How to block negative values in Input tags while entering in forms

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