state = {
    form :[
        {name: 'email', valid: true, value: ''},
        {name: 'password', valid: true, value: ''}
    ]
}

<Button disabled={!this.isValid()}>Submit</Button>

isValid = () =>{
    const { form } = this.state
    let valid = true

    for(let input of form){
        if(input.value === '' || !input.valid)
            valid = false
    }
    return valid
}