The typical initial default argument to be passed to the function using fn.apply

Question

The typical initial default argument to be passed to the function using fn.apply

Recently, I discovered the power of using fn.apply() in JavaScript to store function calls with all their arguments intact for future use.

In my specific situation, I don't require the first argument, which is the context (this), and I want to find a way to exclude passing the this object altogether while still making it clear in my code that I'm not utilizing .apply() for that purpose.

Initially, I considered passing in null, but after reading on MDN:

If the method is a function in non-strict mode code, null and undefined will be replaced with the global object, and primitive values will be boxed.

This leads me to believe that using null or even false may not be recommended. What would serve as an appropriately falsy, empty, or otherwise distinct placeholder value to effectively replace the need for the first argument in fn.apply()?

javascript

Answer 1

Answer №1

It appears that suggesting not to pass null or even false is not the best practice

Actually, it's not entirely true. While using false as a value for this might seem strange, the real issue MDN is cautioning against is with sloppy-mode functions. Here are some examples:

function sloppy() {
    console.log(this);
}
function strict() {
    "use strict";
    console.log(this);
}
sloppy.call(null); // <Window> (or whatever the global object is)
sloppy.call(false); // Boolean {}
strict.call(null); // null
strict.call(false); // false

If you stick to using strict mode, you will be on the safe side. And don't be surprised if you're unable to retrieve primitive this values in sloppy mode functions.

For situations where you need to pass no value, it is recommended to use null or undefined.

Answer 2

It appears that suggesting not to pass null or even false is not the best practice

Actually, it's not entirely true. While using false as a value for this might seem strange, the real issue MDN is cautioning against is with sloppy-mode functions. Here are some examples:

function sloppy() {
    console.log(this);
}
function strict() {
    "use strict";
    console.log(this);
}
sloppy.call(null); // <Window> (or whatever the global object is)
sloppy.call(false); // Boolean {}
strict.call(null); // null
strict.call(false); // false

If you stick to using strict mode, you will be on the safe side. And don't be surprised if you're unable to retrieve primitive this values in sloppy mode functions.

For situations where you need to pass no value, it is recommended to use null or undefined.

The typical initial default argument to be passed to the function using fn.apply

Answer №1

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