I have the following string

output_string = "[10, 10, [1,2,3,4,5], [10,20,30,40,50]]"

Then I JSON.parse it

my_args = JSON.parse(output_string)

How do I unpack it in a Python-like way so that every element in my_args becomes an argument to a JavaScript function?

some_javascript_function(*my_args)开发者_StackOverflow
// should be equivalent to:
some_javascript_function(my_args[0],my_args[1],my_args[2],my_args[3])
// or:
some_javascript_function(10, 10, [1,2,3,4,5], [10,20,30,40,50])

Is there a core JavaScript idiom that does that?

Once you 've collected the function arguments in an array, you can use the apply() method of the function object to invoke your predefined function with it:

   some_javascript_function.apply(this, my_args)

The first parameter (this) sets the context of the invoked function.

You can achieve that by doing this some_javascript_function(...my_args)

This is called spread operation (as unpacking is in python). view docs here https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Spread_operator

Unpack using "..."

The same way you accept unlimited args, you can unpack them.

let vals = [1, 2, 'a', 'b'];

console.log(vals);    // [1, 2, "a", "b"]
console.log(...vals); // 1 2 "a" "b"

Example: Accept unlimited arguments into a function

It will become an array

const someFunc = (...args) => {
    console.log(args);    // [1, 2, "a", "b"]
    console.log(args[0]); // 1
    console.log(...args); // 1 2 "a" "b"
}

someFunc(1, 2, 'a', 'b');

Example: Send array of arguments into a function

const someFunc = (num1, num2, letter1, letter2) => {
    console.log(num1);    // 1
    console.log(letter1); // "a"
}

let vals = [1, 2, 'a', 'b'];
someFunc(...vals);

Send arguments