Check whether a string matches a regex in JS – Dev

The best answers to the question “Check whether a string matches a regex in JS” in the category Dev.

QUESTION:

I want to use JavaScript (can be with jQuery) to do some client-side validation to check whether a string matches the regex:

^([a-z0-9]{5,})$

Ideally it would be an expression that returned true or false.

I’m a JavaScript newbie, does match() do what I need? It seems to check whether part of a string matches a regex, not the whole thing.

ANSWER:

Use test() method :

var term = "sample1";
var re = new RegExp("^([a-z0-9]{5,})$");
if (re.test(term)) {
    console.log("Valid");
} else {
    console.log("Invalid");
}

ANSWER:

Use regex.test() if all you want is a boolean result:

console.log(/^([a-z0-9]{5,})$/.test('abc1')); // false

console.log(/^([a-z0-9]{5,})$/.test('abc12')); // true

console.log(/^([a-z0-9]{5,})$/.test('abc123')); // true

…and you could remove the () from your regexp since you’ve no need for a capture.

ANSWER:

Use /youregexp/.test(yourString) if you only want to know whether your string matches the regexp.

ANSWER:

You can use match() as well:

if (str.match(/^([a-z0-9]{5,})$/)) {
    alert("match!");
}

But test() seems to be faster as you can read here.

Important difference between match() and test():

match() works only with strings, but test() works also with integers.

12345.match(/^([a-z0-9]{5,})$/); // ERROR
/^([a-z0-9]{5,})$/.test(12345);  // true
/^([a-z0-9]{5,})$/.test(null);   // false

// Better watch out for undefined values
/^([a-z0-9]{5,})$/.test(undefined); // true