javascriptwebspeech-api

How do I find parameters declared in a function?

I'm working on the web speech api for my own projects. I'm confused by this function:

colors.forEach(function(v, i, a){
  console.log(v, i);
  colorHTML += '<span style="background-color:' + v + ';"> ' + v + ' </span>';
});

I understand that v, i & a are parameters, but I can't see where they are declared. They are used in the function and I want to understand how they are used.

Many thanks

Edit: parameters within the parentheses

Solution

  • How do I find parameters declared in a function?

    By reading the documentation.

    but I can't see where they are declared

    They are declared right there in the function expression that creates the function you pass as a callback.

    They get values when the function is called.

    arr.forEach(callback(currentValue [, index [, array]])[, thisArg])

    So v is the current value being looped over, i is its index in the array, and a is the array itself.