Why does the HTML input with type "number" allow the letter 'e' to be entered in the field?

html

input-validation

javascript-validation

web-development

byNikita Barsukov·Nov 11, 2024

The letter e is allowed in HTML input type="number" for representing scientific notation, like 1e6 (equivalent to 1000000). To limit the input to integer values, use the pattern attribute with pattern="\d*", deterring non-numeric entries.

Here's an example:

<input type="number" pattern="\d*" title="Input should be a numeric value">

Strategy for managing unwanted characters

In controlling the user’s numerical input, the following methods can come handy:

Pattern attribute: Use this attribute to create a simple validation for numeric input.
```
<input type="text" pattern="[0-9]*" title="Only numbers allowed">
```

JavaScript validation: For complex inputs, you can use JavaScript to create customized validation rules.

inputElement.addEventListener('input', function(event) {
  // This line needs your number, it's lonely without them
  if (/[^0-9]/.test(this.value)) {
    this.value = this.value.replace(/[^0-9]/g, '');
  }
});

Change of type: If you want to prevent users from typing non-numeric characters, consider using type="text" with pattern attribute and JavaScript.
```
<input type="text" onkeypress="return event.keyCode !== 69" title="Please press numbers only, they are feeling left out">
```

Keypress event handling: You can prevent the entry of certain keys using key codes or event.code.

inputElement.addEventListener('keydown', function(event) {
  // 'e' shall not pass!!!
  if (event.key === 'e' || event.key === 'E') {
    event.preventDefault();
  }
});

Deeper into input mechanics

Familiarize yourself with the operations of input type="number":

Clipboard actions: Handle pasted values, as they may include the 'e' character. Employ clipboard API to monitor and validate data before pasting.

inputElement.addEventListener('paste', function(event) {
  // Spying on your clipboard
  let paste = (event.clipboardData || window.clipboardData).getData('text');
  if (paste.match(/[^0-9]/)) {
    event.preventDefault();
  }
});

Browser compatibility: Various browsers might handle inputs differently, so ensure to validate your inputs across many browser environments.
Feedback on user error: If the input is not valid, provide feedback to the users to ensure they understand how to correct their input.

Extend control over numerical input

For granular management of user input, keep these in mind:

Inline event handling: To quickly prevent certain keys, you can handle keypress directly on your HTML.
Numeric validation: Try converting input to a number and check if it's NaN (Not a Number) to validate the input.
Key and control codes: Cater for navigation keys like arrows, backspace, etc. to maintain a good user experience.
Pasting and Drag/Drop: Using clipboard and drag events, you can monitor and cleanse pasted/dropped data before it's filled to the input field.