function randomPonyInRace() {
Ê const pony = { name: 'Rainbow Dash' };
Ê const position = 2;
Ê // ...
Ê return { pony, position };
}
const { pony } = randomPonyInRace();
And you will only have the pony!
2.6. Default parameters and values
One of the characteristics of JavaScript is that it allows developers to call a function with any
number of arguments:
• if you pass more arguments than the number of the parameters, the extra arguments are
ignored (well, you can still use them with the special arguments variable, to be accurate).
• if you pass fewer arguments than the number of the parameters, the missing parameter will be
set to undefined.
The last case is the one that is the most relevant to us. Usually, we pass fewer arguments when the
parameters are optional, like in the following example:
function getPonies(size, page) {
Ê size = size || 10;
Ê page = page || 1;
Ê // ...
Ê server.get(size, page);
}
The optional parameters usually have a default value. The OR operator will return the right
operand if the left one is undefined, as will be the case if the parameter was not provided (to be
completely accurate, if it is falsy, i.e 0, false, "", etc.). Using this trick, the function getPonies can
then be called:
getPonies(20, 2);
getPonies(); // same as getPonies(10, 1);
getPonies(15); // same as getPonies(15, 1);
This worked alright, but it was not really obvious that the parameters were optional ones with
default values, without reading the function body. ES6 introduces a more precise way to have
default parameters, directly in the function definition:
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