How do I write function called validate(z) which takes a string as argument & return true if contain 1 "@" symbol & at least 1 "." & false otherwise

Question

I have just started to learn functions and am finding it quite difficult.

How do I write a function called validate(z) which takes a string as an argument and returns true if it contains one "@" symbol and at least one dot "." and false otherwise.

E.g. if z = "stack@overflow.co.uk" the function will return true.

How about using google? http://stackoverflow.com/questions/1789945/how-can-i-check-if-one-string-contains-another-substring :) — Tom Doodler, Aug 24 '15 at 17:13
i do but i would prefer to not only be given the answer but actually explain each part of the function so i can understand it clearer. — Chris Hapeshis, Aug 24 '15 at 17:15
yes i have done other types of functions but i have never done this sort of thing before — Chris Hapeshis, Aug 24 '15 at 17:19
Does the order matter? Like there should be a dot after the @? — Andre Calil, Aug 24 '15 at 19:41
no, just one @ symbol and at least one dot should appear true. If not then false — Chris Hapeshis, Aug 24 '15 at 20:15

Alan Kis · Answer 1 · 2015-08-24T19:38:27.680

Simplest way is using indexOf()

var s = "foo@foocom";
alert(s.indexOf("@") > -1 && s.indexOf(".") > -1); // Will return false

var s = "foo@foo.com";
alert(s.indexOf("@") > -1 && s.indexOf(".") > -1); // Will return true

Edit: You can't call indexOf() with multiple statements, you have to call it for each character, and then compare that both returns > -1.

Or you can use match() with RegEx.

var string = 'foo@bar.com';

function validate(z) {
    var num_matches_at_sign = (z.match(/@/g) || []).length;
    var num_matches_dot_sign = (z.match(/./g) || []).length;
    if ( num_matches_at_sign == 1 && num_matches_dot_sign >= 1 ) {
        alert(true);
    } else {
        alert(false);
    };
};

validate(string);

Function and whole code is simple and straightforward. First we define function validate(z){...} which takes string z as parameter. We than assign number of occurrences to our variables num_matches_at_sign and num_matches_dot_sign. To count number of occurrences of specified character in a string we use match() method in combination with a regex. In that case our regular expression is /@/g which means that we search for occurrences of the character (or letter) @, and g is modifier, which means global, so we look for all occurrences of the sign @. We user same principle to find number of occurrences of . character. Than we compare that num_matches_at_sign is exactly equal to 1 and num_matches_dot_sign is equal or greater than 1. If both conditions are true (that's why we use && or logical and operator) function return true, otherwise false. You can notice use of logical || operator near match() function, otherwise our match method would return null.

How is it possible you can use multiple statements _inside_ the indexOf function call? Shouldnt you call indexOf twice? — Mark Knol, Aug 24 '15 at 19:00
You are right, you should call indexOf() twice, for each character. — Alan Kis, Aug 24 '15 at 19:05

How do I write function called validate(z) which takes a string as argument & return true if contain 1 "@" symbol & at least 1 "." & false otherwise

1 Answers1