for 循环参数在 JavaScript 中无法正常工作

Question

Hello: I'm new programming. My problem is that the evaluation in the for sentence is not working properly.

With: salir='n' it works correctly
With: salir=='n' don't works.

Thanks

<script type="text/javascript">
    var tabla="";
    var numusuario=0;
    var min=0;
    var max=9;
    var salir='s';
    numusuario=prompt("Escribe un número entre 0 y 9: ");
    for(var j=1;salir='n';j++) 
    {
        if(numusuario<0 || numusuario>=10)
        {
            salir='s';
            numusuario=prompt("Escribe un número entre 0 y 9: ");
        }
        else
        {
            for(var x=min;x<=max;x++)
            {
                tabla = tabla + x + " x " + numusuario + " = " + (x*numusuario) + "\n";
            }
            alert(tabla);
            break;
        }
    }
</script>

Answer 1

salir='n' means assignments. it is always return true

salir=='n' means comparision. it is return false because salir='s' so s is not equal to n

Answer 2

Several things happenning here, but main is that you are mixing different forms of flow control:

• You are using salir (exit, for non-spanish speakers) as a loop end indicator, but...
• The loop condition is always true (as salir='n' evaluates to 'n' , which is true)
• You are using also a variable, j , with no use (you do nothing with it, it doesn't participate in the loop condition neither)
• The only posibility of exiting the loop is the break sentence, which exists the loop.

As the expected behaviour is not clear to me, I cannot assume a solution, but if it is to keep running until the user writes a valid number, then write the multiplication table of that number, it could be:

<script type="text/javascript">
    var tabla="";
    var numusuario=0;
    var min=0;
    var max=9;
    var salir = 'n';

    do {
        numusuario=prompt("Escribe un número entre 0 y 9: ");
        if(numusuario>0 && numusuario<10) {
            for(var x=min;x<=max;x++)
            {
                tabla = tabla + x + " x " + numusuario + " = " + (x*numusuario) + "\n";
            }
            alert(tabla);
            salir = 's';
        }
    } while(salir == 'n')


</script>

The do {} while () executes at least once and checks the condition at the end, that seems better suited in this case, we drop the j variable and use the salir variable as flow control until the user writes the correct number.