在JavaScript中将字符串转换为数组名称

Question

my Goal is to be able to create a function that you can give a string as an argument, and be able to make an array that I could add Items to. You can see my attempt here, but it doesn't seem to work. aka, if I want to make a list name GroceryList, it returns GroceryList, but when I want to add an item to it, it says GroceryList is not defined.

function removeInstance(list, item){
  for(var i = 0; i < list.length; i++){
    if(item === list[i]){
      list.splice(i, 1);
      console.log(list);
      break;
    }
  }
}
function makeList(name){
  name = [];
  console.log(name);
  return name;
}
function removeAllItems(list, item){
  for(var i = 0; i < list.length; i++){
    if(item === list[i]){
      list.splice(i, 1);
      i--;
    }
  }
  console.log(list);
}
function addItem(list, item){
    list.push(item);
    console.log(list);
}

any help would be awesome. Thanks!

Answer 1

Parameters in JavaScript functions are passed by value, not reference; therefore, when you do something like this

var foo = 'bar';

function makeList(name){
  name = [];
  console.log(name);
  return name;
}

makeList(foo);
console.log(foo); // shows 'bar'

you are not modifying the variable which was declared outside the function. Changes to a parameter only affect that local function and not the original variable.

At any rate, I cannot think of any possible scenario where you would need such a makeList function. If you need an array, just create one - there is no need for this!

Answer 2

You need a scope in which you create this array. Suppose you put the JavaScript in an HTML page and you want the array to be in the global scope, then you can create the array as a property of the window object:

function makeList(name){
   window[name] = [];
   return window[name];
}

You can use it like this:

    var arr = makeList("myList");
    myList.push("hello");
    alert('item 0 = ' + myList[0]);