Default Parameters

One of the features added in ES6 is the ability to use default parameters. Default parameters allow parameters to have a predetermined value in case there is no argument passed into the function or if the argument is undefined when called.

Take a look at the code snippet below that uses a default parameter:

  • In the example above, we used the = operator to assign the parameter name a default value of 'stranger'. This is useful to have in case we ever want to include a non-personalized default greeting!
  • When the code calls greeting('Nick') the value of the argument is passed in and, 'Nick', will override the default parameter of 'stranger' to log 'Hello, Nick!' to the console.
  • When there isn’t an argument passed into greeting(), the default value of 'stranger' is used, and 'Hello, stranger!' is logged to the console.

By using a default parameter, we account for situations when an argument isn’t passed into a function that is expecting an argument.