- 5Specify this using .call() or .apply()2m 52s
Specify this using .call() or .apply()
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A function's this argument is usually set implicitly, depending on how the function is called. Ordinary function calls, method calls, and constructor calls all lead to a different this value.
We can also call a function with an explicit this argument using Function.prototype.call() or Function.prototype.apply(). Both methods accept a thisArg as their first parameter and a variable number of additional arguments.
This lesson shows how to use call() and apply() and explains how they differ.
Great video, but I have a question. At the last part of the video, you said about a gotcha about using apply or call without strict mode, but, isn't it an issue for everything, not only apply and call?
Since the usage of strict mode makes it been undefined, and the opposite makes it global.
@Klaus: You're right, outside of strict mode, this is set to the global object when you make a plain function call like func().
The gotcha I was referring to is that if you pass null or undefined to call() or apply() outside of strict mode, these values will be ignored and the global object will be used as well. If you explicitly use call() or apply() in the first place, this is most likely not what you intended.
@Marius: Oh. Got that now!