How to check if a string array contains one string in JavaScript?

I have a string array and one string. I'd like to test this string against the array values and apply a condition the result - if the array contains the string do "A", else do "B".

How can I do that?

There is an indexOf method that all arrays have (except Internet Explorer 8 and below) that will return the index of an element in the array, or -1 if it's not in the array:

if (yourArray.indexOf("someString") > -1) {
    //In the array!
} else {
    //Not in the array
}

If you need to support old IE browsers, you can polyfill this method using the code in the MDN article.

You can use the indexOfmethod and "extend" the Array class with the method contains like this:

Array.prototype.contains = function(element){
    return this.indexOf(element) > -1;
};

with the following results:

["A", "B", "C"].contains("A") equals true

["A", "B", "C"].contains("D") equals false

var stringArray = ["String1", "String2", "String3"];

return (stringArray.indexOf(searchStr) > -1)

Create this function prototype:

Array.prototype.contains = function ( needle ) {
   for (var i in this) { // Loop through every item in array
      if (this[i] == needle) return true; // return true if current item == needle
   }
   return false;
}

and then you can use following code to search in array x

if (x.contains('searchedString')) {
    // do a
}
else
{
      // do b
}

This will do it for you:

function inArray(needle, haystack) {
    var length = haystack.length;
    for(var i = 0; i < length; i++) {
        if(haystack[i] == needle)
            return true;
    }
    return false;
}

I found it in Stack Overflow question JavaScript equivalent of PHP's in_array().