B4J Code Snippet [BANano]: Sharing the goodness

Mashiane · Sep 22, 2020

For Loops

The For Each Loop (the variable type on the loop should be defined)

B4X:

write("For Each Loop<br /> ")
    Dim appNames() As String = Array("b4a", "b4i", "b4j", "b4r")
    For Each appName As String In appNames
        write(appName)
        write("<br />")
    Next
    write ("Exiting from the loop!")

Output

The Counter Loop

B4X:

write("Counter For Loop<br /> ")
    '
    Dim x As Int = 10
    Dim y As Int
    For y = 1 To x
        write($"y: ${y}"$)
        write("<br />")
   Next
    write ("Exiting counter loop!")

Output

The Step Down Loop

B4X:

Dim x As Int = 10
    Dim y As Int
    For y = 10 To 1 Step -1
        write($"y: ${y}"$)
        write("<br />")
    Next
    write ("Exiting step counter loop!")

Mashiane · Sep 22, 2020

Exiting & Skipping Loops

This is based on a condition

1. Here we exit as soon as the counter is 5

B4X:

write("Starting Do Loop ")
        
    Do Until (count = 10)
        write($"Current Count : ${count}<br />"$)
        count = count + 1
        '*****
        If count = 5 Then Exit
    Loop
   
    write("Loop stopped!")

Output

2. Here we skip and process the next loop line as soon as the item is 6

B4X:

Dim b As Int = 0
    For b = 1 To 10
        If b = 6 Then
            Continue
        End If
        document.write($"Item: ${b}</br>"$)   
    Next

output

Mashiane · Oct 4, 2020

A helper class to add a BANanoElement in any parent element.

B4X:

Sub AddElement(parentID As String, tag As String, id As String) As BANanoElement
    Dim el As BANanoElement = BANano.GetElement($"#${parentID}"$).Append($"<${tag} id="${id}"></${tag}>"$).Get($"#${id}"$)
    Return el
End Sub

Usage

B4X:

AddElement("body", "h1", "myh1").SetText("h1. Neumorphism UI heading")

Meaning:

Find the #body element, append to it a h1 element, set the id of the newly created h1 element to myh1, then set the text to "h1. Neomorphism UI heading

Mashiane · Jul 29, 2021

Check if your browser storage is marked for persistent storage?

B4X:

Sub BANano_Ready
    Dim canPersist As Boolean = BANano.Await(BANano.Navigator.GetField("storage").RunMethod("persisted", Null))
    Log(canPersist)
    
    'pgIndex.Init
End Sub

Mashiane · Jul 29, 2021

Request browser storage persistence

B4X:

'request persistence
    Dim isPersisted As Boolean = BANano.Await(BANano.Navigator.GetField("storage").RunMethod("persist", Null))
    Log($"Persisted storage granted: ${isPersisted}"$)

Mashiane · Aug 17, 2021

RunRecursive

B4X:

'run a recursive method
Sub RunRecursive(data As Map, path As String) As Object
    Dim prevObj As BANanoObject = data
    Dim items As List = BANano.Split(".", path)
    Dim iTot As Int = items.Size
    Dim iCnt As Int
    '
    Dim strprev As String = ""
    Dim prtObj As BANanoObject
    Dim litem As String = items.Get(iTot - 1)
    '
    For iCnt = 1 To iTot - 1
        'get the previos path
        strprev = items.Get(iCnt - 1)
        'the parent object
        prtObj = prevObj.GetField(strprev)
        'this does not exist, return
        If BANano.IsUndefined(prtObj) Then
            Return Null
        Else
            prevObj = prtObj
        End If
    Next
    Dim res As Object = prevObj.RunMethod(litem, Null).Result
    If BANano.IsUndefined(res) Then
        res = Null
    End If
    Return res
End Sub

Example code.. this executes a .RunMethod on the last path element delimited by .

Example Code

B4X:

Dim lat As Double = BANanoShared.RunRecursive(place, "geometry.location.lat")
    Dim lng As Double = BANanoShared.RunRecursive(place, "geometry.location.lng")

Ta!

Mashiane · Sep 19, 2021

B4X:

#if javascript
function dataURItoBlob(dataURI) {
    // convert base64/URLEncoded data component to raw binary data held in a string
    var byteString;
    if (dataURI.split(',')[0].indexOf('base64') >= 0)
        byteString = atob(dataURI.split(',')[1]);
    else
        byteString = unescape(dataURI.split(',')[1]);

    // separate out the mime component
    var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];

    // write the bytes of the string to a typed array
    var ia = new Uint8Array(byteString.length);
    for (var i = 0; i < byteString.length; i++) {
        ia = byteString.charCodeAt(i);
    }

    return new Blob([ia], {type:mimeString});
}
#End If

'convert a dataURI to blob for form data
Sub dataURItoBlob(sDataURI As String) As BANanoObject
    Dim out As BANanoObject = BANano.RunJavascriptMethod("dataURItoBlob", Array(sDataURI))
    Return out
End Sub

Mashiane · Nov 16, 2021

Hex to RGB and back

B4X:

#if javascript
function rgbToHex(r, g, b) {
  return "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
}

function hexToRgb(hex) {
  var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
  if(result){
      var r= parseInt(result[1], 16);
      var g= parseInt(result[2], 16);
      var b= parseInt(result[3], 16);
      return r+","+g+","+b;//return 23,14,45 -> reformat if needed 
  } 
  return null;
}
#End If

'convert RGB to HEX
Sub RGBToHex(r As Int, g As Int, b As String) As String
    Dim sout As String = BANano.RunJavascriptMethod("rgbToHex", Array(r, g, b))
    Return sout    
End Sub

'convert HEX to RGB
Sub HexToRGB(hexValue As String) As String
    Dim sout As String = BANano.RunJavascriptMethod("hexToRgb", Array(hexValue))
    Return sout    
End Sub

Mashiane · Feb 5, 2022

'build URLSearchParams from a Map (used with BANanoFetch)

B4X:

Sub URLSearchParamsFromMap(params As Map) As BANanoObject
    Dim obj As BANanoObject
    obj.Initialize2("URLSearchParams", params)
    Return obj
End Sub

build a URLQueryString from Map

B4X:

Sub URLQueryStringFromMap(params As Map) As String
    Dim sb As StringBuilder
    sb.Initialize 
    For Each k As String In params.Keys
        Dim v As String = params.Get(k)
        k = banano.EncodeURIComponent(k)
        v = banano.EncodeURIComponent(v)
        sb.Append($"${k}=${v}&"$)
    Next
    Dim sout As String = sb.ToString
    sout = BANanoShared.RemDelim(sout, "&")
    Return sout
End Sub

Mashiane · Mar 22, 2022

'Showing browser notifications...

B4X:

'show the browser notification
Sub ShowBrowserNotification(Title As String, Desc As String, Url As String, Icon As String, Vibrate As Boolean, Seconds As Int)        'ignoreDeadCode
    'get the notification oject
    Dim notif As BANanoObject = BANano.Window.GetField("Notification")
    'check the permission
    Dim permission As String = notif.GetField("permission").Result
    If permission <> "granted" Then
        'requestPermission
        Dim resp As String = BANano.Await(notif.RunMethod("requestPermission", Null))
        If resp <> "granted" Then Return
    End If
    
    Dim Options As Map = CreateMap()
    Options.Put("icon", Icon)
    Options.Put("body", Desc)
    Options.Put("vibrate", Vibrate)
    '
    Dim n As BANanoObject
    n.Initialize2("Notification", Array(Title, Options))
    Dim showEvent As String = "notification_show"
    Dim closeEvent As String = "notification_close"
    Dim errorEvent As String = "notification_error"
    Dim clickEvent As String = "notification_click"
    
    If SubExists(EventHandler, showEvent) Then
        n.AddEventListener("show", BANano.CallBack(EventHandler, showEvent, Null), False)
    End If
    If SubExists(EventHandler, clickEvent) Then
        n.AddEventListener("click", BANano.CallBack(EventHandler, clickEvent, Null), False)
    End If
    If SubExists(EventHandler, errorEvent) Then
        n.AddEventListener("error", BANano.CallBack(EventHandler, errorEvent, Null), False)
    End If
    If SubExists(EventHandler, closeEvent) Then
        n.AddEventListener("close", BANano.CallBack(EventHandler, closeEvent, Null), False)
    End If
    'close after
    Dim cbClose As BANanoObject = BANano.callback(Me, "CloseNotification", Array(n))
    Dim Sec As Int = Seconds * 1000
    BANano.Window.SetTimeout(cbClose, Sec)
End Sub


private Sub CloseNotification(n As BANanoObject)            'ignoreDeadCode
    n.RunMethod("close", Null)
End Sub

Mashiane · Nov 10, 2022

Table Pagination Script in JavaScript

B4X:

"use strict";

var paginate = function paginate(items) {
  var page = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 1;
  var perPage = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 10;
  var offset = perPage * (page - 1);
  var totalPages = Math.ceil(items.length / perPage);
  var paginatedItems = items.slice(offset, perPage * page);
  return {
    previousPage: page - 1 ? page - 1 : null,
    nextPage: totalPages > page ? page + 1 : null,
    total: items.length,
    totalPages: totalPages,
    items: paginatedItems
  };
};

Mashiane · Jun 30, 2023

I needed code to remove an item from a select HTML5 element by value.

Here is what worked for me... (the banano way)

B4X:

Sub removeByValue(value As String)
    'get the options of the select
    Dim xOptions As Object = mElement.GetField("options")
    'convert the HTMLCollection to array
    Dim a As BANanoObject
    a.Initialize("Array")
    Dim aOptions As List = a.RunMethod("from", xOptions)
    'find the size of the array
    Dim aTot As Int = aOptions.Size - 1
    Dim aCnt As Int = 0
    For aCnt = 0 To aTot
        'get each option
        Dim optionx As BANanoObject = aOptions.Get(aCnt)
        'get the value
        Dim k As String = optionx.GetField("value").Result
        'if the value matches remove the item
        If k.EqualsIgnoreCase(value) Then
            mElement.RunMethod("remove", aCnt)
        End If
    Next
End Sub

Mashiane · Jun 30, 2023

I needed a way to find an Index of an item in a select HTML element by value, the BANano way...

B4X:

Sub findIndexByValue(value As String) As Int
    'get the options of the select
    Dim xOptions As Object = mElement.GetField("options")
    'convert the HTMLCollection to array
    Dim a As BANanoObject
    a.Initialize("Array")
    Dim aOptions As List = a.RunMethod("from", xOptions)
    'find the size of the array
    Dim aTot As Int = aOptions.Size - 1
    Dim aCnt As Int = 0
    For aCnt = 0 To aTot
        'get each option
        Dim optionx As BANanoObject = aOptions.Get(aCnt)
        'get the value
        Dim k As String = optionx.GetField("value").Result
        'if the value matches return the index
        If k.EqualsIgnoreCase(value) Then
            Return aCnt
        End If
    Next
    'the item is not found
    Return -1
End Sub

Mashiane · Aug 13, 2023

How can I paginate an array of objects in JavaScript? - Tutorials / Programming tips

In this post, will take an array of objects and paginate it using JavaScript. Depending on your needs sometimes you may wish to create a…

arjunphp.com

Mashiane · Aug 21, 2023

Get the HTML inside a <template> tag item.

Use <template> to hold some content that will be hidden when the page loads.

B4X:

'get the content of a template
Sub getTemplate As String
    Dim clon As BANanoObject = mElement.RunMethod("cloneNode", True)
    Dim fc As String = clon.GetField("firstElementChild").GetField("outerHTML").result
    Return fc
End Sub

Mashiane · Sep 13, 2023

HTML Input Validation with JavaScript | Aleksandr Hovhannisyan

Validate user input in real time with the checkValidity, reportValidity, and setCustomValidity methods.

www.aleksandrhovhannisyan.com

Mashiane · Jan 11, 2024

Ensure that BANano.GetFile??? always retrieves the last updated resource bypassing the cache.

I just picked up that this kind of call sometimes uses the cached content of the file you want to read from assets or otherwise. To ensure that one is able to get the latest content just append "?" & DateTime.Now to the url.

B4X:

Dim fileContents As Map = banano.Await(banano.GetFileAsJSON(strComp & "?" & DateTime.now, Null))

Now things work like a charm.

B4J Code Snippet [BANano]: Sharing the goodness

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