Get numbers from user

It's not really practical to force a user to enter a number.

It is, however fairly easy to check the input, either immediately it is entered or when trying to perform calculations.

This code demonstrates how it can be done, using a function toFloat

get number.js

// global
var edt1,edt2,edt3,edt4
//Called when application is started.
function OnStart()
{
    //Create a layout
    var lay = app.CreateLayout( "linear", "FillXY" );    
 
    //Create 4 textEdits and add them to layout.
    edt1 = app.CreateTextEdit( "",-1,-1,"Number" );
    edt1.SetHint("Number");
    lay.AddChild( edt1 );
    edt2 = app.CreateTextEdit( "",-1,-1,"Number" );
    edt2.SetHint("Multiply by");
    lay.AddChild( edt2 ); 
    edt3 = app.CreateTextEdit( "",-1,-1,"Number" );
    edt3.SetHint("Divide by");
    lay.AddChild( edt3 );
    edt4 = app.CreateTextEdit( "",-1,-1,"Number" );
    edt4.SetHint("Add");
    lay.AddChild( edt4 );
 
    //Create a "Calculate" button
    var btn = app.CreateButton("Calculate");
    btn.SetOnTouch(btnOnTouch);
    lay.AddChild(btn);
    //Add layout to app.    
    app.AddLayout( lay );
    
}
 
function btnOnTouch()
{
    var res = toFloat(edt1)
        * toFloat(edt2)
        / toFloat(edt3)
        + toFloat(edt4);
    if(isNaN(res)) app.Alert("The result is not a valid number")
    else app.Alert(res);
}
 
function toFloat(control) 
{
//take a control (probably a TextEdit) and return its text as a number
    var value = control.GetText();
    var ret = +(value.replace(',','.'));
    if( isNaN(ret) ) app.ShowPopup(value +" is not a number");
    return ret;
}