Why are my React form submission values undefined? - reactjs

Question

I'm trying to create a form and store the values of it in state – so far, so reasonable.
I think I've set it all up right, but when I return the contents of state, each and every field comes back undefined. I don't doubt that there's something simple I've overlooked in setting it up, but I can't for the life of me see what it is...
Can someone put me out of my misery?
handleAddProperty = (event) => {
event.preventDefault();
console.log(this.state.fields);
console.log(this.state.fields.type);
};
handleFieldChange = (event) => {
this.setState({
fields: {
title: event.target.value.title,
type: event.target.value.type,
bedrooms: event.target.value.bedrooms,
bathrooms: event.target.value.bathrooms,
price: event.target.value.price,
city: event.target.value.city,
email: event.target.value.email,
},
});
};
render() {
return (
<div className="addproperty">
<form onSubmit={this.handleAddProperty}>
<button type="submit">Add</button>
<input name="title" value={this.state.fields.title} onChange={this.handleFieldChange} />
<select name="type" value={this.state.fields.type} onChange={this.handleFieldChange}>
<option value={this.state.fields.type}>Flat</option>
<option value={this.state.fields.type}>Detached</option>
<option value={this.state.fields.type}>Semi-Detached</option>
<option value={this.state.fields.type}>Terraced</option>
<option value={this.state.fields.type}>End of Terrace</option>
<option value={this.state.fields.type}>Cottage</option>
<option value={this.state.fields.type}>Bungalow</option>
</select>
<input name="bedrooms" value={this.state.fields.bedrooms} onChange={this.handleFieldChange} />
<input name="bathrooms" value={this.state.fields.bathrooms} onChange={this.handleFieldChange} />
<input name="price" value={this.state.fields.price} onChange={this.handleFieldChange} />
<select name="city" value={this.state.fields.city} onChange={this.handleFieldChange}>
<option value={this.state.fields.city}>Manchester</option>
<option value={this.state.fields.city}>Leeds</option>
<option value={this.state.fields.city}>Sheffield</option>
<option value={this.state.fields.city}>Liverpool</option>
</select>
<input name="email" value={this.state.fields.email} onChange={this.handleFieldChange} />
</form>
</div>
);
}
}

Answer 1

You should access to event.target.value rather then to event.target.value[key] because handleFieldChange function triggers for each input field (when they change their state) and for each of that triggers event.targetis referring to a different input field (basically the input which has been changed).
To update the state you can use event.target.name as a key to your form object members inside the component state. The code might look like the following:
constructor(props) {
super(props);
this.state = { form: { name: 'Jane' } };
}
handleFieldChange(event) {
// This will update specific key in your form object inside the local state
this.setState({
form: Object.assign({}, this.state.form, {
[event.target.name]: event.target.value,
}),
});
}
<input
name="test"
type="text"
onChange={e => this.handleFieldChange(e)}
/>