Note: This is an updated answer. Comments below refer to an old version which messed around with keycodes.
JavaScript
Try it yourself on JSFiddle.
You can filter the input values of a text <input>
with the following setInputFilter
function (supports Copy+Paste, Drag+Drop, keyboard shortcuts, context menu operations, non-typeable keys, the caret position, different keyboard layouts, and all browsers since IE 9):
// Restricts input for the given textbox to the given inputFilter function.
function setInputFilter(textbox, inputFilter) {
["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
textbox.addEventListener(event, function() {
if (inputFilter(this.value)) {
this.oldValue = this.value;
this.oldSelectionStart = this.selectionStart;
this.oldSelectionEnd = this.selectionEnd;
} else if (this.hasOwnProperty("oldValue")) {
this.value = this.oldValue;
this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
} else {
this.value = "";
}
});
});
}
You can now use the setInputFilter
function to install an input filter:
setInputFilter(document.getElementById("myTextBox"), function(value) {
return /^\d*\.?\d*$/.test(value); // Allow digits and '.' only, using a RegExp
});
See the JSFiddle demo for more input filter examples. Also note that you still must do server side validation!
TypeScript
Here is a TypeScript version of this.
function setInputFilter(textbox: Element, inputFilter: (value: string) => boolean): void {
["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
textbox.addEventListener(event, function(this: (HTMLInputElement | HTMLTextAreaElement) & {oldValue: string; oldSelectionStart: number | null, oldSelectionEnd: number | null}) {
if (inputFilter(this.value)) {
this.oldValue = this.value;
this.oldSelectionStart = this.selectionStart;
this.oldSelectionEnd = this.selectionEnd;
} else if (Object.prototype.hasOwnProperty.call(this, 'oldValue')) {
this.value = this.oldValue;
if (this.oldSelectionStart !== null &&
this.oldSelectionEnd !== null) {
this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
}
} else {
this.value = "";
}
});
});
}
jQuery
There is also a jQuery version of this. See this answer.
HTML 5
HTML 5 has a native solution with <input type="number">
(see the specification), but note that browser support varies:
- Most browsers will only validate the input when submitting the form, and not when typing.
- Most mobile browsers don't support the
step
, min
and max
attributes.
- Chrome (version 71.0.3578.98) still allows the user to enter the characters
e
and E
into the field. Also see this question.
- Firefox (version 64.0) and Edge (EdgeHTML version 17.17134) still allow the user to enter any text into the field.
Try it yourself on w3schools.com.
Looking at the Apple, Mozilla and Mozilla again documentation, the functionality seems to be limited to handle only string key/value pairs.
A workaround can be to stringify your object before storing it, and later parse it when you retrieve it:
var testObject = { 'one': 1, 'two': 2, 'three': 3 };
// Put the object into storage
localStorage.setItem('testObject', JSON.stringify(testObject));
// Retrieve the object from storage
var retrievedObject = localStorage.getItem('testObject');
console.log('retrievedObject: ', JSON.parse(retrievedObject));
Best Answer
Because that's exactly how the spec says it should work. The number input can accept floating-point numbers, including negative symbols and the
e
orE
character (where the exponent is the number after thee
orE
):