Clash Royale CLAN TAG#URR8PPP

How to call this default args function more than once?

I have encountered a question where I need to allow default args to be set on a function in JavaScript:

function dfltArgs(func, params)

const strFn = func.toString()
console.log(strFn)
const args = /(([^)]+))/.exec(strFn)[1].split(',')

const defaultVal = (arg, val) => typeof arg !== 'undefined' ? arg : val

return (...dynamicArgs) =>
const withDefaults = args.map((arg, i) =>
defaultVal(dynamicArgs[i], params[args[i]]))
return func(...withDefaults)




function add (a, b) return a + b
var add_ = dfltArgs(add,b:9)
console.log(add_(10)) // Should be 19
var add_ = dfltArgs(add_,b:3)
console.log(add_(10)) // Should now be 13

However, I need to be able to call this function more than once and overwrite previously set defaults:

var add_ = defaults(add,b:9)
add_(10) // Should be 19
var add_ = defaultArguments(add_,b:3)
add_(10) // Should now be 13


This does not work in my implementation, because the stringified function on the second call is: (...dynamicArgs) => {, etc.

(...dynamicArgs) => {

How can I refactor this? Probably need to use bind somehow?

bind

Function.bind()

var add = function( x, y ) return x + y; ; var add5 = add.bind( null, 5 );

1 Answer
1

Instead of your complicated default args thing, why not just use some arrow functions with real default arguments:

var _add = (a, b = 8) => add(a, b);


That way you can easily change the bound things:

var add_ = (a = 2, b) => _add(a, b);
add_() // 10


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