Map array values to function parameters

Problem

You want to map values of an array to function parameters in ES5.

Ingredients

• 1 function
• 1 array
• the apply() method

Directions

1. Given: a function that takes different parameters and an array containing concrete arguments.

   function add(x, y, z) {
     return x + y + z;
   }
   var parameters = [2, 3, 4];

2. Naive solution, but also very verbose: access array values by index.

   var result = add(
     parameters[0],
     parameters[1],
     parameters[2]
   );
   console.log(result);  // 9

3. Better to use the apply() method (at least when you are in ES5).

   ...
   var parameters = [2, 3, 4];
   var result = add.apply(null, parameters);
   console.log(result);  // 9

4. Voilá, there you got a perfect mapping from array values to function parameters.

Alternative recipes

• Since ES2015: use the spread operator, which can be used to map array values to function parameters:

  ...
  let parameters = [2, 3, 4];
  let result = add(...parameters);
  console.log(result);  // 9