setting a variable to be used in function

Question

I have function like this:

var name_regex = /^[a-zA-Z0-9_ -]{3,32}$/,
body_regex = /^[a-zA-Z0-9_ -]$/,
email_regex = /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/,
phone_regex = /^[0-9-]{3,32}$/,
error_count;
function validation_test (name, value) {
 var test_name = name + '_regex';
 console.log(test_name);
 error_count = 0;
 if(!test_name.test(value)){
 error_count += 1;
 }
}

And if I try to run it (on submit) I get following error:

test_name.test is not a function

console.log(test_name) is giving me the proper name for the variable (for example name_regex). How can I make this variable work?

• JohnnyHK: So test_name contains the name of a function you want to run?
• clentfort: You could try window[test_name] if it is defined in the global scope. Else namespace[test_name] where namespace is the namespace where the variable to test are defined in.
• Ram: test is one of the methods of regular expression object, not the string.
• Sasha: Added the rest of the code to be clear what I want

Answer 1

Just use an object:

var regexes = {
 name: /^[a-zA-Z0-9_ -]{3,32}$/,
 body: /^[a-zA-Z0-9_ -]$/,
 email: /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/,
 phone: /^[0-9-]{3,32}$/
};
function isValid(name, value) {
 return regexes[name].test(value);
}

In your other code:

 if( !isValid( "phone", 123 ) ) {
 alert("Invalid phone");
 }

• clentfort: Well he could simply use window[test_name] if he wants to.
• Christian Mann: There are a lot of ways to accomplish the same task in Javascript, yes. I would never recommend the above one.
• Esailija: @Sasha you are resetting error_count to 0 every time validation_test is called, is that intentional?
• Sasha: Yes, because if there is there is an error, error_count will be 1, but if all goes well error_count will be 0 (there is JQuery each function which checks each required field). Is this good method to do, or I am doing it wrong?
• Esailija: @Sasha well it's very confusing because the whole error_count is useless then. You might as well return true or false because you are not keeping any count, the result is always either 0 or 1 which is better expressed by false and true

Answer 2

Are you trying to call the function e.g.

validation_test('phone', '9184079201');

If so, I'd recommend putting your regular expressions into an object:

var regex = {
 'name': '...',
 'body': '...',
 'email': '...',
 'phone': '...',
};
function validation_test(name, value) {
 if(!regex[name].test(value)) {
 //...
 }
}

That way you can look them up by string.

• Sasha: This method is also working, but Esailija was first to give an answer, so I can only give you an upvote :(. Nevertheless, thank you for your help. There is nothing wrong with more knowledge :)

Answer 3

variable test_name should be proper regExp object https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/RegExp/test

consider

...
function validation_test (name, value) {
 var test_name = name + '_regex';
 console.log(typeof(test_name)); // string
...

Than happen because of concatenation on the line above console log

• dmi3y: you are welcome, and I guess correct answer would be because you pass string name as well. So probably string conversion is another option did not really looked details on this stackoverflow.com/questions/874709/… but looks like constructive
• dmi3y: oh sorry, that's not case, it is just another thing:)

Answer 4

test_name is a string, not the regex it represents, so !test_name.test(value) won't do what you want.

Since you're not using name anywhere else in the function, why don't you just pass the regex in as an argument?

function validation_test (test_name, value) {
 error_count = 0;
 if(!test_name.test(value)){
 error_count += 1;
 }
}