Access variable by string inside function

Question

I want to check out whether the arguments provided in a function are strings and for this I'm using the following condition:

function someFunction (variable1, variable2, variable3) {
   ["variable1", "variable2", "variable3"].forEach(function (each) {
      if (!(/*something*/[each].constructor.name === "String")) throw new TypeError(
         each + " must be a string. " + /*something*/[each].constructor.name +
         " was given instead."
      );
      else ...
   });
}

Had the check occurred in the global namespace, I could've used window[each], since variables are properties of window, like below:

var variable1, variable2, variable3;

["variable1", "variable2", "variable3"].forEach(function (each) {
   if (!(window[each] instanceof String)) throw new TypeError(
      each + " must be a string. " + window[each].constructor.name + " was given instead."
   );
   else ...
});

How can the above be achieve inside a function?

There's no way to access local variables by name. window[name] can only be used with global variables, there's nothing equivalent for local variables. — Barmar
– Barmar, Commented Aug 30, 2016 at 18:42

baao · Accepted Answer · 2016-08-30 18:47:06Z

1

You only want to allow strings, right? If so - use arguments, typeof and the code below:

function someFunction(variable1, variable2, variable3) {
    [].forEach.call(arguments, function(each) {
        console.log(typeof each);
        if (typeof each != 'string') {
            throw new TypeError(
                each + " must be a string. " + /*something*/ each.constructor.name +
                " was given instead."
            );
        } else {
            console.log("its a string")
        }
    });
}

someFunction("foo", "bar", ["baz"])

edited Aug 30, 2016 at 18:47

answered Aug 30, 2016 at 18:14

baao

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Comments

Angel Politis · Accepted Answer · 2016-08-30 18:38:37Z

1

inside forEach, each loops over the variables

function someFunction (variable1, variable2, variable3) {
   [variable1, variable2, variable3].forEach(function (each) {
      if (!(each.constructor.name === "String")) throw new TypeError(
         each + " must be a string. " + each.constructor.name +
         " was given instead."
      );
      else ...
   });
}

edited Aug 30, 2016 at 18:38

Angel Politis

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answered Aug 30, 2016 at 18:14

Jerome WAGNER

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2 Comments

Jerome WAGNER Over a year ago

Fixed to use the variables. Not sure what OP is asking for.

Angel Politis Over a year ago

Your answer works fine @JeromeWAGNER. I edited the condition inside if, because it only accepted strings created through String().

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