Can only use get without the set in Object.defineProperty?

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I need more information about attributes get and set of the method Object.defineProperty().

I understood that get calls a function when a property is read and that set calls a function when a value is saved to a property.

Can I use one without the other? For example, define the get without defining the set?

javascript

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2 answers

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1

Yes you can, that way makes the effect of a property read only.

I mean, it works to have only one getter:

var obj = {_valA: 0, _valB:0};
Object.defineProperty(obj, 'valA', { // exemplo A
    get: function() {
        return this._valA;
    }
});
Object.defineProperty(obj, 'valB', { // exemplo B
    get: function() {
        return this._valB;
    },
    set: function(value) {
        this._valB = value;
    }
});
console.log(obj.valA); // 0
obj.valA = 10;
console.log(obj.valA); // 0 <- não mudou o valor
console.log('-------')
console.log(obj.valB); // 0
obj.valB = 10;
console.log(obj.valB); // 10 <- mudou o valor com o setter

(jsFiddle: https://jsfiddle.net/h3ju37ga/)

but in that case most correct would be to have a read-only property, read-only and in that case you should do so:

var obj = {};
Object.defineProperty(obj, 'val', {
    enumerable: true,
    writable: false,
    value: 5
});

console.log(obj.val); // 5
obj.val = 10;
console.log(obj.val); // 5 <- não muda o valor

jsFiddle: https://jsfiddle.net/avgah0ko/

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