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I'm new to javascript , I'm trying learning how functions etc in JS and trying to add 2 numbers
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>JS ADD</title>
</head>
<body>
<h1>Funcitons is JS</h1>
<input type="number" id="num1">
<input type="number" id="num2">
<button type="button" onclick="addNumAction()">
Add
</button>
<script>
function addNum(n1, n2) {
return parseInt(n1) + parseInt(n2);
}
function addNumAction() {
var n1 = document.getElementById("num1").value;
var n2 = document.getElementById("num2").value;
var sum = addNum(n1, n2);
window.alert("" + sum);
}
</script>
</body>
</html>I'm new to javascript , I'm trying learning how functions etc in JS and trying to add 2 numbers
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>JS ADD</title>
</head>
<body>
<h1>Funcitons is JS</h1>
<input type="number" id="num1">
<input type="number" id="num2">
<button type="button" onclick="addNumAction()">
Add
</button>
<script>
function addNum(n1, n2) {
return parseInt(n1) + parseInt(n2);
}
function addNumAction() {
var n1 = document.getElementById("num1").value;
var n2 = document.getElementById("num2").value;
var sum = addNum(n1, n2);
window.alert("" + sum);
}
</script>
</body>
</html>If I remove the parseInt() the value is treated as a string only , then what is the point of using <input type="number"> ?please explain to me.
what field to use for getting input as a number?
- w3.org/TR/html5/forms.html#number-state-(type=number) - see the spec – Arun P Johny Commented Mar 4, 2016 at 9:04
- there is nothing you can do. HTML Input element is documented to return the value in String type representing number. See my explanation below. – secretgenes Commented Mar 4, 2016 at 9:30
10 Answers
Reset to default 76It's normal you get a string.
The purpose of the number type is that mobile browsers use this for showing the right keyboards and some browsers use this for validation purposes. For example the email type will show a keyboard with the @ and '.' on the keyboard and number will show a numeric keyboard.
Neither HTML nor HTTP really have the concept of data types (possibly because they aren't programming languages to begin with) and everything is a string. When you use another language to reach that information you may sometimes get some amount of magic as a feature (for instance, PHP will generate arrays from GET/POST fields that have paired square brackets on their names) but that's a feature of such other language.
In this case, .value belongs to the DOM API and such API does have types. But let's see how it's defined. The <input> tag is represented by the HTMLInputElement interface and the value property is of type DOMString:
DOMString is a UTF-16 String. As JavaScript already uses such strings, DOMString is mapped directly to a String.
In other words, type="number" is a hint to implement client-side validation and appropriate GUI controls but the underlying element will still store strings.
You can use valueAsNumber (described on that page) to get the actual number value. So your code would then be:
function addNum(n1, n2) {
return n1 + n2;
}
function addNumAction() {
var n1 = document.getElementById("num1").valueAsNumber;
var n2 = document.getElementById("num2").valueAsNumber;
var sum = addNum(n1, n2);
window.alert("" + sum);
}
tl;dr you're doing everything correctly already, just keep using parseInt.
type="number" tells the browser that the user should only be allowed to enter number characters, but deep down, it's still a text field.
HTML Input elements are documented to return string representing a number. See the documentation here : Documentation of HTML Input
When you set input type="number" then these input field don't accept non numeric input but at the same time it doesn't make the input value type "number". The reason is inputted number contain digits as a subset of the valid characters, but they also contain completely non-numeric characters like spaces, hyphens and parenthesis.
Use valueAsNumber
Non-numbers can still be input. Make sure to check for validity, and handle mistakes.
const value = myInput.valueAsNumber
if (isNaN(value)) return // or other handling
If you require updates on every change:
myInput.addEventListener("change", () => {
const newValue = myInput.valueAsNumber
if (isNan(newValue)) return
// Handle change
})
You can also try to convert a number string into a number by using the + operator:
const ns = '3'
console.log(typeof ns)
console.log(typeof +ns)Or you can safely convert only if it is able to do so:
const ns = '3'
const s = 'hello'
const toNum = v => !!+v ? +v : v
console.log(typeof toNum(ns))
console.log(typeof toNum(s))The above snippet uses + to convert a value to a number. If it is unable to do so, +v returns NaN. It then use ! to convert NaN into a boolean and then use another ! to negate the boolean.
type="number" only for browser validation. But you get a string. And you may use parseInt(num1) or + before string.
function addNum(n1, n2) {
return +(n1) + +(n2);
}
If you are using variables in your html, try the following:
<input type="number" (focusout)="(modifiedVal = +modifiedVal)" value="modifiedVal">
Here, modifiedVal is the variable and '+' before variable converts the variable into number.
You can use a method to block non-numbers.
HTML
<iput type="number" onkeypress="blockNonNumbers($event)"/>
Javascript
blockNonNumbers(event: KeyboardEvent) {
const charCode = (event.which) ? event.which : event.keyCode;
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
event.preventDefault();
}
}
本文标签： HTML input typequotnumberquot still returning a string when accessed from javascriptStack Overflow
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