how to fill some input with the option of a select using javascript?

I have this view and I would like to know how to fill the inputs when I select the option of the select that is from a foreign table, in the option of the select is the foreign key and another attribute of the table, but I do not know how to put that information of the inputs when the select option is selected.

This is the code.

@extends('layouts.app1')
    @section('content')

    <div class="col-md-8 col-md-offset-2">
        @if (count($errors) > 0)
        <div class="alert alert-danger">
            <strong>Error!</strong> Revise los campos obligatorios.<br><br>
            <ul>
                @foreach ($errors->all() as $error)
                <li>{{ $error }}</li>
                @endforeach
            </ul>
        </div>
        @endif
        @if(Session::has('success'))
        <div class="alert alert-info">
            {{Session::get('success')}}
        </div>
        @endif
        <div class="panel panel-default">
            <div class="panel-heading">
                <h3 class="panel-title">Nuevo Mantenimiento</h3>
            </div>
            <div class="panel-body">
                <div class="table-container">
                    <form method="POST" action="{{ route('mantenimiento_pc.store') }}"  role="form">
                        {{ csrf_field() }}
                        <div >
                            <label for="computador_id">ID Computador:</label>
                            <select class="form-control input-sm" name="computador_id" id="computador_id"  onchange="selecOp(event.target.value)">>
                                <option disabled="true" selected="true">=== Select PC===</option>
                                @foreach($computador as $computadores)
                                <option modelo-pc="{{$computadores->modelo_pc}}" marca-pc="{{$computadores->marca_pc}}" value="{{$computadores->id}}">{{$computadores->nombre_pc}}</option>
                                @endforeach
                            </select>
                        </div>
                        <div>
                            <label for="marca_equipo">Marca Equipo:</label>
                            <input type="text" name="marca_equipo" class="form-control input-sm" placeholder="Marca" id="marca_equipo" />

                        </div>
                        <div>
                            <label for="modelo">Modelo:</label>
                            <input id="modelo" class="form-control input-sm" type="text" placeholder="Modelo"  />
                        </div>
                        <div>
                            <label for="motivo">Motivo:</label>
                            <textarea type="text" name="motivo" id="motivo" cols="50" rows="10" class="form-control input-sm" placeholder="Motivo" style="resize: none"></textarea>
                        </div>

                        <div>
                            <label for="diagnostico">Diagnostico:</label>
                            <textarea type="text" name="diagnostico" id="diagnostico" cols="50" rows="10" class="form-control input-sm" placeholder="Diagnostico" style="resize: none"></textarea>
                        </div>
                        <div>
                            <input type="submit"  value="Guardar" class="btn btn-success btn-block">
                            <a href="{{ route('mantenimiento_pc.index') }}" class="btn btn-info btn-block" >Atrás</a>

                        </div>
                        <script>
                            var valorEnvio = ""
                            function selecOp(marca_pc) {


                                document.getElementById("marca_equipo").value = marca_pc,//declararle el valor del select al input
                                document.getElementById("modelo").value 
                            }
                            function obtenerValor() {
                                marca_pc = document.getElementById("marca_equipo").value //obtener valor del input
                                valorEnvio = marca//declarar valor a la variable a usar en el ajax
                                console.log(valorEnvio)
                           }



                        </script>
                </div>
            </div>

        </div>
    </div>
    @endsection