Can't make my Mutation work in vue apollo client [duplicate] - vue.js

Question

I'm running into the problem, that Vue converts the value of an input field of type number into a string and I just can't figure out why. The guide I am following along does not run into this issue and get's the values as numbers, as expected.
The vue docs state, that Vue would convert the value to a number, if the type of the input is number.
The code is originated from a component, but I adjusted it to run in JSFiddle: https://jsfiddle.net/d5wLsnvp/3/
<template>
<div class="col-sm-6 col-md-4">
<div class="panel panel-success">
<div class="panel-heading">
<h3 class="panel-title">
{{ stock.name }}
<small>(Price: {{ stock.price }})</small>
</h3>
</div>
<div class="panel-body">
<div class="pull-left">
<input type="number" class="form-control" placeholder="Quantity" v-model="quantity"/>
</div>
<div class="pull-right">
<button class="btn btn-success" #click="buyStock">Buy</button>
</div>
</div>
</div>
</div>
</template>
<script>
export default {
props: ['stock'],
data() {
return {
quantity: 0 // Init with 0 stays a number
};
},
methods: {
buyStock() {
const order = {
stockId: this.stock.id,
stockPrice: this.stock.price,
quantity: this.quantity
};
console.log(order);
this.quantity = 0; // Reset to 0 is a number
}
}
}
</script>
The quantity value is the issue.
It is initialized with 0 and when I just press the "Buy" button, the console shows:
Object { stockId: 1, stockPrice: 110, quantity: 0 }
But as soon as I change the value by either using the spinners or just type in a new value, the console will show:
Object { stockId: 1, stockPrice: 110, quantity: "1" }
Tested with Firefox 59.0.2 and Chrome 65.0.3325.181. Both state that they are up to date. I actually also tried it in Microsoft Edge, with the same result.
So what am I missing here? Why is Vue not converting the value to a number?

Answer 1

You need to use .number modifier for v-model, like this:
<input v-model.number="quantity" type="number">
Note: empty string ('') is not converted to a number, so you may need to handle it separately.

Answer 2

Change the order object to :
const order = {
stockId: this.stock.id,
stockPrice: this.stock.price,
quantity: +this.quantity
};
This will automatically parse the string to a number.
In general the data from HTML inputs are strings. The input type only checks if a valid string has been provided in the field.