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Keff
Keff

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Private Object & Class Properties

#javascript #snippets

Easy and clean way of creating private object methods and properties, making use of Symbols

// Object with private field function privateProps() { const priv = Symbol('private prop'); return { [priv]: { id: '1111-2222-3333-4444' }, getSomething() { return fetch(`http://.../users/${this[priv].id}`); } } } const obj = privateProps(); obj.getSomething(); // Accesible obj[priv] // 'undefined' as we don't have access to priv,  // we can't re-create the symbol from outside as it is unique.
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Using in a class?

I don't like this pattern that much, but it can be useful in some cases.
There are other ways of accomplishing this, this is just one example.

const MyClass = (() => { const priv = Symbol('private'); return class { constructor(name) { this[priv] = name; } getName(){ return this[priv]; } } })(); let instance = new MyClass('test'); instance.private; // undefined instance.priv; // undefined instance.getName(); // 'test'
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Currently there is a proposal for adding private fields to classes, check it out here

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