JavaScript has a ton of weird little gotchas. GitHub1s is an open source project, which is not officially provided by GitHub.
One example: JavaScript cannot handle 64 bit integers. This page is NOT officially provided by GitHub. Is the function called with new ( new binding)? If so, this is the newly constructed object. JavaScript can be weird and it's good to know that, because you may run into these things and waste a lot of time. Ask these questions in this order, and stop when the first rule applies. Now, we can summarize the rules for determining this from a function call's call-site, in their order of precedence. While that distinction may not be a terribly common need everyday coding, it's important to fully understand how all these parts of the mechanism interact, so we have an accurate set of rules to analyze and predict its outcome.
Call it with new, and you always get the newly constructed object back, regardless of if the function was previously hard-bound. Why is new being able to override hard binding useful? Imagine a function that you are given (might be hard-bound, might not, you don't know), and you want to use that function but not cause any side-effects on any object it may have been hard-bound to. We won't actually dive into explaining how this trickery works (it's complicated and beyond our scope here), but essentially the snippet determines whether or not the bound function has been called with new (resulting in a newly constructed object being its this), and if so, it uses that new this rather than the previously specified hard binding for this. The part that's doing the task (allowing new overriding) is: this instanceof fNOP & Recent commits have higher weight than older ones. Activity is a relative number indicating how actively a project is being developed. Stars - the number of stars that a project has on GitHub.Growth - month over month growth in stars.
You-Dont-Know-JS/this & object prototypes/ch2.md at master įunction foo () var aArgs = (arguments, 1),Īncat((arguments)) The number of mentions indicates the total number of mentions that weve tracked plus the number of user suggested alternatives.