TIL: Today I learned...

Today I learned that there is a truncate table SQL command that deletes all data from a database table like Delete from but is faster and uses fewer system and transaction log resources. It’s supported in most database engines but there are likely caveats to keep in mind. For instance, with SQL Server: It will reseed identity columns You can’t truncate tables that referenced in constraints and it requires ALTER table privileges For clearing out data in lower environments though, I’ve found it useful.

I’ve recently been learning about the new logical properties in CSS. Essentially if we’re developing applications for a global audience, instead of thinking in terms of right/left or top/bottom, we should start thinking in terms of “inline” and “block”. These let us specify our styling and layouts in relative logical values instead of physical ones so they can adapt appropriately for right-to-left or vertical languages. For example, margin-left: 20px would now be margin-inline-start: 20px. ...

Today I learned about the git maintenance command that runs tasks for regular maintenance of a git repo. If you run git maintenance start in a repo, git will create scheduled tasks to run at regular intervals to perform these tasks in the background like garbage collection. This will optimize and speed up the repo without having to tack them on occasionally as you run other commands. A particularly handy task it will run every hour is prefetch, where it does a git fetch but only pulls down the data and doesn’t update any refs. Then when you actually run git fetch or git pull, it completes almost instantly because it already has all the data. ...

Today I learned that the isNaN global function in javascript isn’t very useful for validating numbers. The main reason is that it returns false for an empty string since it coerces it to 0. To add to the confusion, Number.isNaN() behaves slightly differently since it just checks for the value NaN. For validation, I found Number.isInteger() to be the most useful.

Today I learned that ORIG_HEAD is a reference that git maintains to the previous commit HEAD pointed to before it “was modified in a drastic way”. The docs mention these operations as examples of when ORIG_HEAD is updated: (git am, git merge, git rebase, git reset) This is useful when you want to undo one of those operations. You can use git reset --hard ORIG_HEAD (or --keep) to put your branch back to where it was before the operation.

This is probably a very niche use case, but I learned today that you can abbreviate commands that git populates in the todo list during an interactive rebase. So instead of this: pick deadbee The oneline of the commit pick fa1afe1 The oneline of the next commit It’ll look like this: p deadbee The oneline of the commit p fa1afe1 The oneline of the next commit You can enable this with git config --global rebase.abbreviateCommands true. ...

Today I learned about the font-variant-numeric CSS property that lets you control alternate glyphs for numbers. Not every font will support all of these but the tabular-nums option is common and seems especially useful for data in grids. Using Font Variant Numeric

Today I learned that there’s a new javascript array method that returns a new array with the element at the given index replaced with the given value. Convenient for manipulating array values without mutating the original array. const arr = [1, 2, 3, 4, 5]; console.log(arr.with(2, 6)); // [1, 2, 6, 4, 5] console.log(arr); // [1, 2, 3, 4, 5]

Today I learned that you can add //# sourceURL=<anything>.js special comment to an inline script tag to have it show up as a separate javascript file in the dev tools sources tab. This makes it a bit easier to work with especially when you have a huge inline script tag you’re dealing with. It even works with eval() too if you’re unfortunate enough to be dealing with that. ...

Today I learned that there is a Content-Security-Policy (CSP) directive connect-src that you can use to restrict all outgoing requests from your website to only the domains that you specify. This is a powerful mitigation against any kind of script injection attacks since no data can then be exfiltrated from your page. It applies to XMLHttpRequest (AJAX), WebSocket, fetch(), <a ping> or EventSource. CSP is an HTTP response header for enhancing the security of a site and there are of course several other directives you might want to enable. ...