I would like a JavaScript function to have optional arguments which I set a default on, which gets used if the value isn't defined. In Ruby you can do it like this:
def read_file(file, delete_after = false)
# code
end
function read_file(file, delete_after = false) {
// Code
}
From ES6/ES2015, default parameters is in the language specification.
function read_file(file, delete_after = false) {
// Code
}
just works.
Reference: Default Parameters - MDN
Default function parameters allow formal parameters to be initialized with default values if no value or undefined is passed.
Pre ES2015,
There are a lot of ways, but this is my preferred method - it lets you pass in anything you want, including false or null. (typeof null == "object"
)
function foo(a, b)
{
a = typeof a !== 'undefined' ? a : 42;
b = typeof b !== 'undefined' ? b : 'default_b';
...
}