How to search a string for all values contained in an Array of strings? (Javascript)

Question

I am trying to learn if there is a javascript method to search a string to see if that string contains any of the values in an array of strings.

An example would be:

var a = 'How now brown cow';
var b = new Array('red', 'green', 'brown');

The resulting function would return true because the word brown is contained within the string a .

More specifically what I am trying to do (except using values from form input) is:

var a = '[email protected]';
var b = new Array('.com', '.net', '.org');

This should also return true. Then based on this I will go on to accept var a as valid.

My actual code as of right now (which always returns null) is as follows:

function check_domain(){
  for(var i=0; i<domains.length; i++){
    var d = domains[i];
    if(elemen.value.indexOf(d) != d){
      return null;
    }
    else{
      vEmail.style.visibility = 'visible';
    }
  }
}

  window.domains = new Array(....Array values here....);

BTW, you shouldn't really use the window object for storing variables. — Jivings
– Jivings, Commented Feb 16, 2012 at 0:43
Fyi, the [...] syntax is preferred over the new Array(...) syntax unless you want to create a new array with a certain amount of undefined elements (in which case you would use new Array(n) for n elements). Besides that, your code leaks globals, for example, you should really use var i in the check_domain() function - you really do not want any loop variable to become global! — ThiefMaster
– ThiefMaster, Commented Feb 16, 2012 at 1:01
@ThiefMaster I fixed the var i issue, but the Array is not empty, i just left it empty and wrote what I did because it has over 100 strings in it that took up a lot of space irrelevant to the question. — person0
– person0, Commented Feb 16, 2012 at 1:15
@Jivings why not? and what should I do to avoid it. My code has a lot of this going on because I'm using the addEventListener method to call all functions. Any time a user clicks on the page all information about that element is stored as elemen; when they click something else the value of elemen automatically changes to the new element clicked. Should I just declare the variables as global variables and use them like that? I'm getting confused cause people keep telling me not to use global variables but I don't know how the heck to avoid it and still acomplish the purposes of my code. — person0
– person0, Commented Feb 16, 2012 at 1:24
Sorry PTBN :) You'd be better to just declare them with var at the top of scope. If you're interested in improving your JavaScript then take a look at closures and self invoking functions to control scope. — Jivings
– Jivings, Commented Feb 16, 2012 at 9:04

Guffa · Accepted Answer · 2012-02-16 00:43:32Z

2

You can create a regular expression from the array:

var re = new RegExp(domains.join('|').replace(/\./g,'\\.'));

Then you can test a string:

var a = '[email protected]';
var found = re.test(a);

answered Feb 16, 2012 at 0:43

Guffa

703k112 gold badges760 silver badges1k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

person0 Over a year ago

Could you further explain join('|') and replace(/\./g,'\\.') please?

Guffa Over a year ago

@Proud_to_be_Noob: The join method makes a string from the array that looks like ".com|.net|.org", then the replace turns each . into \. as that is how you specify a period in a regular expression.

Jivings · Accepted Answer · 2012-02-16 00:31:44Z

1

Not sure why you've got .indexOf(d) != d. Shouldn't it be:

function check_domain(){
   var d, i;
   for(i = 0; i < domains.length; i++){
      d = domains[i];
      if(elemen.value.indexOf(d) != -1) {
        return true;
      }
   }
}

answered Feb 16, 2012 at 0:31

Jivings

23.3k7 gold badges63 silver badges102 bronze badges

1 Comment

person0 Over a year ago

Oh yeah, haha don't know why I did that, my bad, I was thinking of a different method but wrote indexOf instead. Thanks, that fixed the problem.

Delta · Accepted Answer · 2012-02-16 02:26:33Z

0

Yes, there is something called Regular Expressions, if you really need it to match values in an array you can create a loop and check for each word against the string, something like this:

var a = 'How now brown cow';
var b = new Array('red', 'green', 'brown');

function Check(target, lookFor)
{
    for(var I = 0, L = lookFor.length; I <= L; I++)
        if(new RegExp(lookFor[I]).test(target))
            return true;
    return false;
}

alert(Check(a, b));

But in your case, the best way to go about this is just to join all the words you want to look for in the target string inside only one regular expression, so you avoid using a loop.

if(/(\.com|\.net|\.org)$/.test("[email protected]"))
{
// Valid email
}
else
{
// Invalid email
}

edited Feb 16, 2012 at 2:26

answered Feb 16, 2012 at 0:39

Delta

4,3382 gold badges32 silver badges37 bronze badges

2 Comments

ThiefMaster Over a year ago

Any reason you are using uppercase loop variables? While it's mainly a matter of style, I think pretty much everyone uses lowercase i, j, k, ii, jj for loop variables. And I don't think caching the .length value is really necessary - most likely the number of elements in an array is stored so accessing it is O(1) just as accessing the variable where you cached it.

Delta Over a year ago

No reasons at all, I have been doing it like that out of habit but I don't think that is much important right? Same goes to caching the length.

Collectives™ on Stack Overflow

How to search a string for all values contained in an Array of strings? (Javascript)

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related