碎碎念

onChangeText is basically a simplified version of onChange, so you can easily use it, without the hassle of going through event.target.value to get changed value.

So, when should you use onChange and when onChangeText?
If you have simple form with few textinputs, or simple logic, you can go straight away and use onChangeText

<TextInput value={this.state.name} onChangeText={(text) => this.setState({name: text})}>

If you have more complicated forms and/or you have more logic in handling data (like handling text differently from number) when user changes input, then you are better of with onChange, because it gives you more flexibility. For example:

handleChange(event) {
    const {name, type, value} = event.nativeEvent;
    let processedData = value;
    if(type==='text') {
        processedData = value.toUpperCase();
    } else if (type==='number') {
        processedData = value * 2;
    }
    this.setState({[name]: processedData})
}

<TextInput name="username" type="text" value={this.state.username} onChange={this.handleChange}}>
<TextInput name="password" type="number" value={this.state.password} onChange={this.handleChange}}>