将最后一个参数传递给 function - JavaScript

Question

If I have a function with two different parameters, how can I make it so that if I input only one parameter, it will use the input as the second parameter rather than the first parameter? For example, if I have this function:

function x(a=1,b=2) {
    console.log(a);
    console.log(b);
}

and call x(3) , it will use the 3 for a and return "3, 2"

x(3);

=> 3
   2

I want it so that the function instead uses the 3 for the b parameter, and therefore returns "1, 3"

x(3);
=> 1
   3

Answer 1

If you change your method to use a destructured object , you can pass an object with just the properties you wish to and default the rest

 function x({a=1,b=2} = {}){ console.log("a",a); console.log("b",b); } x(); x({a:10}) x({b:20})

Answer 2

Use object destructuring approach

 let a,b; /* * define variable to avoid overwrite in large application */ function x({a=1,b=2} = {}){ console.log( { a } ); console.log( { b } ); } x({b:20}) /* Passed only 'b' here */