Default parameter values have been introduced in ES6 in 2015, and are widely implemented in modern browsers.
This is a doSomething function which accepts param1.
const doSomething = (param1) => {
}
We can add a default value for param1 if the function is invoked without specifying a parameter:
const doSomething = (param1 = 'test') => {
}
This works for more parameters as well, of course:
const doSomething = (param1 = 'test', param2 = 'test2') => {
}
What if you have an unique object with parameters values in it?
Once upon a time, if we had to pass an object of options to a function, in order to have default values of those options if one of them was not defined, you had to add a little bit of code inside the function:
const colorize = (options) => {
if (!options) {
options = {}
}
const color = ('color' in options) ? options.color : 'yellow'
...
}
With destructuring you can provide default values, which simplifies the code a lot:
const colorize = ({ color = 'yellow' }) => {
...
}
If no object is passed when calling our colorize function, similarly we can assign an empty object by default:
const spin = ({ color = 'yellow' } = {}) => {
...
}
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