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I often see that when a function needs to be called with bound parameters in no particular context the undefined is more often than not is preferred over the null as a choice of context, as in:
f.call(undefined, param1, param2)
is preferred over:
f.call(null, param1, param2)
I'm wondering if there is any particular reason for this?
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Only use null if you explicitly want to denote the value of a variable as having "no value". As @com2gz states: null is used to define something programmatically empty. undefined is meant to say that the reference is not existing. A null value has a defined reference to "nothing".
A function returns undefined if a value was not returned . Note: While you can use undefined as an identifier (variable name) in any scope other than the global scope (because undefined is not a reserved word), doing so is a very bad idea that will make your code difficult to maintain and debug.
Definition: Null: It is the intentional absence of the value. It is one of the primitive values of JavaScript. Undefined: It means the value does not exist in the compiler.
In JavaScript, undefined is a type, whereas null an object. It means a variable declared, but no value has been assigned a value. Whereas, null in JavaScript is an assignment value. You can assign it to a variable.
What's the benefit of binding to
undefinedinstead ofnull?
I don't think there is any. From 10.4.3 Entering Function Code:
- If the function code is strict code, set the ThisBinding to thisArg.
- Else if thisArg is null or undefined, set the ThisBinding to the global object.
- ...
So, if the code is not strict, in both cases this will be set to the global object.
But if the code is strict, this will actually either be null or undefined. f could be implemented to distinguish these cases, but that doesn't seem to be a very likely scenario to me.
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