Javascript FORs - differences and similarities in a particular case

StackOverflow https://stackoverflow.com/questions/23381843

  •  12-07-2023
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Question

I have one doubt that arose while I was trying to redirect to another page with submit.

Why if I replace the code for(var i=0;i...;i++) with the line for(i in arreglo), in the redirection (onsubmit) only it shows alert('one') instead of both, alert('one') and alert('two')?

<html>
    <head>
        <title>Registro Javascript</title>
        <meta charset="utf-8"/>
        <script type="text/javascript">
            function inicio(){
                document.getElementById("formulario").onsubmit=verificar;
            }

            function verificar(){
                var arreglo=document.getElementsByTagName("input");
                var camposVacios="";
                var numVacios=0;
                alert('one');
                for(var i=0;i<arreglo.length;i++){
                    if(arreglo[i].getAttribute("type")=="text"){
                        if(arreglo[i].value.length==0){
                            camposVacios+="\n- "+arreglo[i].id;
                            numVacios=numVacios+1;
                        }
                    }
                }
                alert('two');
                if(numVacios>0){
                    alert('Los siguientes campos estan sin completar : '+camposVacios);
                    return false;
                }
                return true;
            }

            function verificarObjeto(objeto){
                if(objeto.value.length==0)
                    alert('El campo '+objeto.id+' debe tener al menos un caracter.');
            }
        </script>
    </head>
    <body onload="inicio()"> <br>
        <form id="formulario" method="post" action="other.html"> <br>
            Nombre : <input type="text" id="nombre" onblur="verificarObjeto(this)"/> <br>
            Apellido Paterno: <input type="text" id="apellido paterno" onblur="verificarObjeto(this)"/> <br>
            Apellido Materno: <input type="text" id="apellido materno" onblur="verificarObjeto(this)"/> <br>

            Edad : <input type="text" id="edad" onblur="verificarObjeto(this)"/> <br>
            Direccion : <input type="text" id="direccion" onblur="verificarObjeto(this)"/> <br>
            Telefono : <input type="text" id="telefono" onblur="verificarObjeto(this)"/> <br>
            Email : <input type="text" id="email" onblur="verificarObjeto(this)"/> <br>
            <input type="submit" value="Registrarse"/>
            <input type="reset" value="Limpiar campos"/>
        </form>
    </body> 
</html>
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Solution

The object you get with .getElementsByTagName is not an array but is a nodeList. You have to turn it to an array before you put it in a loop to use more efficiently and in those cases i prefer .forEach rather than for.

To make the array :

var array = Array.prototype.slice.call(arreglo);

To loop the array

array.forEach(function(elem){
  if(elem.getAttribute("type")=="text"){
  ....

FIDDLE

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