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Destructuring (destructured) parameters in ES6/ES2015


Since I’ve been coding ruby a lot the last couple of years I’m used to defaults in keyword arguments since ruby 2.0. In Javascript this is kinda equal to the use of destructured parameters like this:

const test = ({ param = 'default value' } = {}) => param;

So when running this I’m getting the default value:

test() // 'default value'

But as I’m coming from ruby, that = {} is very easy to forget which doesn’t set the default value:

const test = ({ param = 'default value' }) => param;
test() // TypeError: (destructured parameter) is undefined

When you think about how the destructured parameters work, and realize that the object in the parameters are just a parameter and needs a default value; it make sense. But if you’re just glancing at it quickly, especially coming from ruby it doesn’t really make sense.