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JavaScript

Posted by Sébastien Pennarun
Sébastien Pennarun
4,222 Points

trying to understand window object

I m reviewing a project that consist of two heroes attacking each other turn by turn.

in the project i came across this function:

function majData(action, casterObj, defenderObj) {

const name = action.name === 'mana' || action.name === 'shield' ? action.name : 'normal'

window[${name}Action](action, casterObj, defenderObj) }

can someone explain me in details what the line with the window object do?

i tryed to comment it and it seems it update the life bar and mana bar of my heroes but i cant understand what it does behind the scene.

thanks for your help,

PS: if you need the complete code just tell me

1 Answer

Steven Parker
Steven Parker
230,853 Points
Steven Parker
Steven Parker
230,853 Points

When posting code, use Markdown formatting, like this:

function majData(action, casterObj, defenderObj) {
  const name = action.name === "mana" || action.name === "shield" ? action.name : "normal";
  window[`${name}Action`](action, casterObj, defenderObj);
}

This is a clever little function that constructs another function's name by using the value in "name" attribute of the "action" object. The result will be one of these: "manaAction", "shieldAction", or "normalAction".

It then calls the function with that name and passes along the same arguments that it was given. The role of the window object here is just to allow the use of bracket notation to access the other function by name.

A more conventional way to accomplish the same thing might look like this:

function majData(action, casterObj, defenderObj) {
  if (action.name == "shield") shieldAction(action, casterObj, defenderObj);
  else if (action.name == "mana") manaAction(action, casterObj, defenderObj);
  else normalAction(action, casterObj, defenderObj);
}
Sébastien Pennarun
Sébastien Pennarun
4,222 Points

sorry for the messy post and thanks for your answer. If i understand well the window object provide a "context" in order to make the function call since doing a call as follow isn't correct am i right?

`${name}Action`(action, casterObj, defenderObj)`
Steven Parker
Steven Parker
230,853 Points
Steven Parker
Steven Parker
230,853 Points

That's right, and by itself, `${name}Action` is just a string and not a function identifier.