Eval Method

In This Topic

Description

Evaluates JavaScript code and returns a String result.

Syntax

Visual Basic
Public Function Eval( _ ByVal Code As String _ ) As String

Parameters

Code: The JavaScript code to evaluate.

Return Type

The string result of the evaluation.

The following code is used to stringify the evaluation result:

V8 Value Stringify for Eval	Copy Code
std::wstring V8ValueToString(const CefRefPtr<CefV8Value>& value, const CefRefPtr<CefV8Exception>& exception, std::wstring string_for_null, std::wstring string_for_undefined) { std::wstring result; if (exception.get() && !exception->GetMessageW().empty()) { result = L"__V8_EXCEPTION:" + std::wstring(exception->GetMessageW()); } else { if (value->IsNull()) { result = string_for_null; } else if (value->IsUndefined()) { result = string_for_undefined; } else if (value->IsBool()) { result = value->GetBoolValue() ? L"true" : L"false"; } else if (value->IsUInt()) { result = std::to_wstring(value->GetUIntValue()); } else if (value->IsInt()) { result = std::to_wstring(value->GetIntValue()); } else if (value->IsDouble()) { result = std::to_wstring(value->GetDoubleValue()); } else if (value->IsDate()) { CefTime t = value->GetDateValue(); wchar_t buffer[100]; wsprintf(buffer, L"d-d-d dd", t.year, t.month, t.day_of_month, t.hour, t.minute, t.second); result = buffer; } else if (!value->IsString()) { CComVariant v = V8ValueToVariant(value); v.ChangeType(VT_BSTR); CefRefPtr<CefV8Value> vv = VariantToV8Value(v); result = vv->GetStringValue().ToWString(); } else { result = value->GetStringValue().ToWString(); } } return result; }

V8 Value Stringify for Eval

Copy Code

std::wstring V8ValueToString(const CefRefPtr<CefV8Value>& value,
                             const CefRefPtr<CefV8Exception>& exception,
                             std::wstring string_for_null,
                             std::wstring string_for_undefined)
{
 std::wstring result;
 if (exception.get() && !exception->GetMessageW().empty())
 {
  result = L"__V8_EXCEPTION:" + std::wstring(exception->GetMessageW());    
 }
 else
 {
  if (value->IsNull())
  {
   result = string_for_null;
  }
  else if (value->IsUndefined())
  {
   result = string_for_undefined;
  }
  else if (value->IsBool())
  {
   result = value->GetBoolValue() ? L"true" : L"false";
  }
  else if (value->IsUInt())
  {
   result = std::to_wstring(value->GetUIntValue());
  }
  else if (value->IsInt())
  {
   result = std::to_wstring(value->GetIntValue());
  }
  else if (value->IsDouble())
  {
   result = std::to_wstring(value->GetDoubleValue());
  }
  else if (value->IsDate())
  {
   CefTime t = value->GetDateValue();
   wchar_t buffer[100];
   wsprintf(buffer, L"d-d-d dd", t.year, t.month, t.day_of_month, t.hour, t.minute, t.second);
   result = buffer;
  }
  else if (!value->IsString())
  {
   CComVariant v = V8ValueToVariant(value);
   v.ChangeType(VT_BSTR);
   CefRefPtr<CefV8Value> vv = VariantToV8Value(v);
   result = vv->GetStringValue().ToWString();
  }
  else
  {
   result = value->GetStringValue().ToWString();
  }
 }
 return result;
}

Remarks

For programming languages that support OLE/COM Variant is recommended to use CallByName method instead of Eval.

You can control the returned value for null and undefined values by setting Settings.string_for_null and Settings.string_for_undefined properties during OnCreate event.

V8 JavaScript Evaluation Exceptions are converted to OLE/COM Automation Exceptions.

Example

Example (Visual Basic)
Example (C#)

Private Sub mnuEval_Click()
    On Error Resume Next
    Dim s As String
    s = InputBox("JavaScript")
    If s = "" Then Exit Sub
    s = WebKitX1.Eval(s)
    If s <> "" Then
        MsgBox s, vbInformation
    End If
End Sub

private void menuItemEvalJavaScript_Click(object sender, EventArgs e)
{
    string input = Microsoft.VisualBasic.Interaction.InputBox("JavaScript", "HTML5Pad", "", 500, 300);
    if (input != "")
    {
        WebKitXCEF31.Eval(input);
        if (input != "")
        {
            MessageBox.Show(input, "HTML5 Pad", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
    }
}