What's the difference in writing the empty arrays inside the method instead of writing them as object parameters?

Question

What's the difference in writing the empty arrays inside the method,

var example = {
    calcMethod: function() {
        this.array1 = [];
        this.array2 = [];
    }
};

instead of writing them as object parameters?

var example = {
    array1 : [],
    array2 : []
};

to eventually fill them with data.

Your question is really about the use of the `this` keyword. See [this](https://stackoverflow.com/questions/41496958/this-does-not-work-properly-in-another-event-im-clueless-as-to-why/41496969#41496969). But your specific syntax `let = object` is invalid. It should be something like `let o = {...}` — Scott Marcus, Oct 26 '18 at 17:19

score 2 · Accepted Answer · answered Oct 26 '18 at 17:24

Despite the illegal javascript syntax I'll answer your question.

The difference is that calcMethod must be called before array1 and array2 are defined in the first snippet. Otherwise they'll be undefined:

let object1 = {

calcMethod: function() {
        this.array1 = [1];
        this.array2 = [2];
    }
}

let object2 = {
    array1: [3],
    array2: [4]
}


console.log(object1.array1);  // undefined
console.log(object1.array2);  // undefined

object1.calcMethod();

console.log(object1.array1);  // [1]
console.log(object1.array2);  // [2]

console.log(object2.array1);  // [3]
console.log(object2.array2);  // [4]

Thank you very much @SaniSinghHuttunen I fixed the syntax so anyone with the same question can have a valid answer. — Israel Umaña, Mar 19 '20 at 19:58

What's the difference in writing the empty arrays inside the method instead of writing them as object parameters?

1 Answers1