Update an array only using class methods when the array is private property in class-CodePudding

I am writing a class where I have some data(it could be up to 100K) in form of an array. The data has to be added in a LIFO manner.

class AddProximityValues {
    #values = [];
    
    getValues () {
        return this.#values;
    } 
    
    setValues(...elements) {
        this.#values.push(...elements);
    }
    
    //tried this way not sure
    // if this is the right way of doing this
    getValueEff() {
      return [...this.#values]
    }
}

const addProximityValues = new AddProximityValues();


console.log(addProximityValues.setValues(...[10, 20, 40]));
console.log(addProximityValues.getValues().push(50)); // don't want push to work
console.log(addProximityValues.getValues());


console.log('*********************************');
console.log(addProximityValues.getValueEff().push(50)); // don't want push to work
console.log(addProximityValues.getValues());

From the code when I return the array, it returns the reference and you can write values to it without calling the class function. I want that only the class method can update the values.

One way of doing this is returning a new array from the existing values, but it will take more memory if the array is too big. Is there any way to achieve it in a more efficient way?

CodePudding user response：

One option is not to have getValues return an array at all. It could return an array iterator (or you could even make your class iterable by adding a [Symbol.iterator] function). An iterator provides sequential access to the array values without allowing modification of the array. You could also provide a method for getting a value for a given index, and perhaps even a length property:

class AddProximityValues {
    #values = [];
    
    [Symbol.iterator]() {
        // Return an iterator for the values
        return this.#values[Symbol.iterator]();
    } 

    get(index) {
        return this.#values[index];
    }
    
    get length() {
        return this.#values.length;
    }
    
    setValues(...elements) {
        this.#values.push(...elements);
    }
}

const addProximityValues = new AddProximityValues();

addProximityValues.setValues(...[10, 20, 40]);
// This would fail, no `push` on an iterator
// console.log(addProximityValues.getValues().push(50)); // don't want push to work
// The code using it can loop through
for (const value of addProximityValues) {
    console.log(value);
}
console.log(`Value at index 2: ${addProximityValues.get(2)}`);
console.log(`There are ${addProximityValues.length} values`);
// The code can still get all the values as an array if it really needs to
console.log([...addProximityValues]);