Below, I present some stumbling blocks that I met during developing a mobile, cross-platform, JavaScript-based WebApp.<\/p>\n
Virtually all modern browsers are implementing \u201clocal storage\u201d, a service to store data locally on the device. The localStorage object implements a so-called key-value store. That works cross-platform amazingly well.<\/p>\n
We want to store a date, so we need to transform the date into a string first. To read it back, we need to convert the string to a date object back again. Because JavaScript has a date object since the last century, you expect that it to provides the appropriate functions.<\/p>\n
Surprisingly, the standard methods such as date.parse() are not very helpful. The only defined date format is RFC2822, but this format is optimized for English-language people. A date in this format will look like this:<\/p>\n
\u201cMon, 31 Dec 1995 12:30:00\u201d<\/em><\/p>\n A much better format is defined in ISO 8601. Dates will look like this: “YYYY-MM-DDThh:mmTZD<\/em>“.<\/p>\n The complexity is much lower. No month names or week day names must be parsed, and the fields are in a fixed position. So it is much easier to read and write for computers.<\/p>\n Nevertheless, a call to date.parse() with an ISO date does not work in many devices: in my tests, I got errors on devices with Android 2.1 and 2.3, as well as with a BlackBerry OS6 device. The reverse method Date.toISOString() is also missing. ISO-dates are officially supported only since JavaScript 1.8.5 or ECMAScript version 5.<\/p>\n JavaScript offers built-in functions for simple dialogs:<\/p>\n The dialogs of this methods are presented in the correct platform-specific design automatically. Since there are modal dialogs, the application logic becomes trivial. If we want to ask the user for a string, this simple program line is enough:<\/p>\n username = prompt(‘Your username’);<\/p>\n However, Microsoft decided that the prompt-method is a security problem. Because of this, prompt() is no longer supported<\/a> in Internet Explorer starting with version 7 (in the default setting), and also not in Windows Mobile.<\/p>\n Annoying is that the Windows Mobile browser suppresses the dialog “secretly”. We can not distinguish the result of the suppressed prompt()-call from an empty user input, and so we can no longer react and offer alternatives for text input. So we need to do the unpopular “browser sniffing” again.<\/p>","protected":false},"excerpt":{"rendered":"Dialogs and the prompt-method<\/h3>\n
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