JavaScript Basics: Reflect.apply

ghasemkiani (69)in #javascript • 6 years ago

The method Reflect.apply is just a better and more meaningful way to do Function.prototype.apply. In other words, it allows you to call the given function using a specified context (this argument) on an array of arguments. Here is an example:

    let person = {
        name: "John",
        speak(city) {
            console.log(`Hi. I am ${this.name}. I am calling from ${city}.`);
        },
    };

    let someone = {
        name: "Jack",
    };

    person.speak("Houston");
    // Hi. I am John. I am calling from Houston.
    
    Reflect.apply(person.speak, someone, ["Boston"]);
    // Hi. I am Jack. I am calling from Boston.
    person.speak.apply(someone, ["Boston"]); // the same
    Function.prototype.apply.call(person.speak, someone, ["Boston"]); // the same

As I said in an earlier post, the Reflect object gathers all functionality related to reflection in one place. This makes it possible to write neater and more readable code.

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6 years ago in #javascript by ghasemkiani (69)

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adasq (63) 6 years ago

Last line is really interesting...
Function.prototype.apply.call
Was not aware it works that way. Actually:

Function.prototype.call === Function.prototype.bind.call.apply.bind.call

So it seem that Function.prototype functions (Function.prototype.bind, Function.prototype.call, etc.) do have object linkage to Function.prototypeobject. We can even access such linkage. See here:
Function.prototype.apply.__proto__ === Function.prototype

That's why we can chain it deeply. Really interesting. Also was not aware of such Reflect feature. Thanks for sharing.

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