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Test if something is not undefined in JavaScript
...defined", instead of a useful message about an "un-caught exception @ line 123 of file xyz.js". Eventually a second developer will probably comment out the console.log() statement, making it more difficult for a 3rd developer to come in and fix a bug happening deep within doSomething().
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how to show alternate image if source image is not found? (onerror working in IE but not in mozilla)
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If you're open to a PHP solution:
<td><img src='<?PHP
$path1 = "path/to/your/image.jpg";
$path2 = "alternate/path/to/another/image.jpg";
echo file_exists($path1) ? $path1 : $path2;
?>' alt='' />
</td>
////EDI...
TabLayout 拓展：多模式 Tab 导航组件 · App Inventor 2 中文网
...字号、指示器等均可自定义。
.aix 拓展下载：
cn.fun123.TabLayout.aix
快速使用
顶部 Tab（最常用）
设计器中拖入 TabLayout，设置 Width = Fill parent，Height = Fill parent
创建多个 VerticalArrangement ...
PHPMailer character encoding issues
I try to use PHPMailer to send registration, activation. etc mail to users:
11 Answers
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我帮儿子用App Inventor 2给遥控车装了"蓝牙大脑"，手机一划车就...
...景下比较麻烦，好在我的场景主要是手机单向发送指令，问题不大。
最终效果
成果超出预期：
- 手机放在沙发上，20米内流畅控制（HC-05标称10米，实测无遮挡30米都可控）
- 方向盘实时映射，没有肉眼可见的延迟
- 儿子...
Supabase扩展能实现实时推送吗？源码级Realtime能力分析 - App应用开发 - ...
...研 App Inventor 2 后台推送通知方案时，我们深入分析了 fun123 自研的 Supabase 扩展。Supabase 官方确实提供了 Realtime 实时推送功能，那么当前扩展是否已经封装了这些能力？能否直接用来做推送？
以下是源码级分析结论。
一...
Python + Django page redirect
...direct (e.g. cflocation in ColdFusion, or header(location:http://) for PHP) in Django?
10 Answers
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What is a postback?
...tback is essentially when a form is submitted to the same page or script (.php .asp etc) as you are currently on to proccesses the data rather than sending you to a new page.
An example could be a page on a forum (viewpage.php), where you submit a comment and it is submitted to the same page (viewp...
Preventing form resubmission
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@Rpant on chrome the php file that sends the location header doesn't even show up in the browser history, so the back button simply takes you back to the form.
– FluorescentGreen5
May 5 '17 at 12:03
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Git is ignoring files that aren't in gitignore
...a few other files, but my .gitignore file only has it ignoring a config.php file. Is there some global ignore file somewhere that I can't seem to find? I have to specify files to add them now, and it's giving me this warning:
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