Javascript - Determine if String Is In List

Question

In SQL we can see if a string is in a list like so:

Column IN ('a', 'b', 'c')

What's a good way to do this in javascript? I realize one can use the switch function:

var str = 'a'
var flag = false;

switch (str) {
   case 'a':
   case 'b':
   case 'c':
      flag = true;
   default:
}

if (thisthing || thatthing || flag === true) {
   // do something
}

But this is a horrible mess. It's also clunky to do this:

if (thisthing || thatthing || str === 'a' || str === 'b' || str === 'c') {
   // do something
}

And I'm not sure about the performance or clarity of this:

if (thisthing || thatthing || {a:1, b:1, c:1}[str]) {
   // do something
}

Any ideas?

UPDATE

I didn't think to mention that in this case, I have to use IE as it's for a corporate intranet page. So ['a', 'b', 'c'].indexOf(str) !== -1 won't work.

Note: here's the full version of the indexOf function for browsers that don't support it. And here's my version (since I don't care about list position or traversing in reverse, this should be faster):

if (!Array.prototype.indexOf) {
   Array.prototype.indexOf = function(item) {
      var i = this.length;
      while (i--) {
         if (this[i] === item) return i;
      }
   }
}

Answer 1

Arrays have an indexOf method which can be used to search for strings:

js> a = ['foo', 'bar', 'baz']
foo,bar,baz
js> a.indexOf('bar')
1
js> a.indexOf('quux')
-1

Answer 2

You can call indexOf:

if (['a', 'b', 'c'].indexOf(str) >= 0) {
    //do something
}

Answer 3

In addition to indexOf (which other posters have suggested), using prototype's Enumberable.include() can make this more neat and concise:

var list = ['a', 'b', 'c'];
if (list.include(str)) {
  // do stuff
}

Answer 4

Most of the answers suggest the Array.prototype.indexOf method, the only problem is that it will not work on any IE version.

As an alternative I leave you two more options that will work on all browsers:

if (/Foo|Bar|Baz/.test(str)) {
  // ...
}


if (str.match("Foo|Bar|Baz")) {
  // ...
}

Answer 5

A trick I've used is

>>> ("something" in {"a string":"", "somthing":"", "another string":""})
false
>>> ("something" in {"a string":"", "something":"", "another string":""})
true

You could do something like

>>> a = ["a string", "something", "another string"];
>>> b = {};
>>> for(var i=0; i<a.length;i++){b[a[i]]="";} /* Transform the array in a dict */
>>> ("something" in b)
true

Answer 6

SLaks' answer was a good start, but not "correct" because it doesn't work in IE. While I didn't mention the need for IE in my initial post, he didn't mention his code doesn't work in IE, either.

I eventually used the indexOf() function, and "rolled my own" for IE:

if (!Array.prototype.indexOf) {
   Array.prototype.indexOf = function(item) {
      var i = this.length;
      while (i--) {
         if (this[i] === item) return i;
      }
   }
}