B4X Requires Chilkat v11.4.0+

JavaScript console using Callbacks

See more JavaScript Examples

Demonstrates console output using Chilkat JavaScript with callbacks. B4X

Sub js_ProgressInfo (name As String, value As String)
    Log(name & ": " & value)
End Sub

Sub ChilkatExample

    Dim success As Boolean = False

    '  This example demonstrates using the built-in console object.
    '  The Javascript run in this example is shown below.



    '  Load the JavaScript from a file.
    Dim sbScript As ChilkatStringBuilder
    sbScript.Initialize
    success = sbScript.LoadFile("qa_data/js_tests/test_console.js", "utf-8")
    If success = False Then
        Log(sbScript.LastErrorText)
        Return
    End If


    Dim js As ChilkatJs
    js.Initialize("js")
    Dim result As ChilkatJsonObject
    result.Initialize

    '  Run the JavaScript
    '  Results (not console output) go to result.
    '  Note: Eval returns the completion value of the script. This is generally the value of the last evaluated expression.
    '  In this case, the last evaluated expression is console.log which does not calculate a value. Therefore, it returns undefined.
    success = js.Eval(sbScript, result)
    If success = False Then
        Log(sbScript.LastErrorText)
        Return
    End If


    '  We can look at the result, which is "undefined", which is normal and expected.
    Log(result.Emit)
    '  The result JSON is: {"type":"undefined","value":"undefined"}

    '  The console output is received using ProgressInfo callbacks.
    '  The output is:

    '  log: Hello World, 248, 12.05
    '  
    '  error: foo:bar baz
    '  
    '  warn: 1 2 3
    '  
    '  log: %% %s
    '  
    '  log: myApp: {
    '    "appName": "Example",
    '    "version": 1,
    '    "isDebug": true,
    '    "supportedTypes": [
    '      "string",
    '      "number",
    '      "object"
    '    ],
    '    "settings": {
    '      "maxWidgets": 1024,
    '      "allowIO": true
    '    }
    '  }
    '  
    '  log: App: myApp (Version 1)
    '  
    '  {"type":"undefined","value":"undefined"}

End Sub

JavaScript

// Chilkat Js console emits CRLF line endings on Windows, and LF line endings on non-Windows.

console.log("Hello %s, %d, %f", "World", 248, 12.05);
// Output: Hello World, 248, 12.05

// If there are more arguments than the number of specifiers, the extra arguments are output, separated by spaces:
console.error('%s:%s', 'foo', 'bar', 'baz');
// Output: foo:bar baz

// If the first argument does not contain a valid format specifier, outputs a string that is the concatenation of all arguments separated by spaces:
console.warn(1,2,3);
// Output: 1 2 3

//If only one argument is passed, it is returned as it is without any formatting:
console.log("%% %s");
// Output: %% %s

const myApp = {
    appName: "Example",
    version: 1.0,
    isDebug: true,
    supportedTypes: ["string", "number", "object"],
    settings: {
       "maxWidgets": 1024,
        allowIO: true
    }
};

// %O: Emits the same as JSON.stringify(myConfig, null, 2)
console.log("myApp: %O", myApp);
// Output:
// myApp: {
//   "appName": "Example",
//   "version": 1,
//   "isDebug": true,
//   "supportedTypes": [
//     "string",
//     "number",
//     "object"
//   ],
//   "settings": {
//     "maxWidgets": 1024,
//     "allowIO": true
//   }
// }

console.log("App: %s (Version %d)", myApp.appName, myApp.version);
// Output: App: Example (Version 1)