Check whether a string matches a regex in JS


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.

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");
}

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

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


 let str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
 let regexp = /[a-d]/gi;
 console.log(str.match(regexp));

I would recommend using the execute method which returns null if no match exists otherwise it returns a helpful object.

let case1 = /^([a-z0-9]{5,})$/.exec("abc1");
console.log(case1); //null

let case2 = /^([a-z0-9]{5,})$/.exec("pass3434");
console.log(case2); // ['pass3434', 'pass3434', index:0, input:'pass3434', groups: undefined]

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.


Here's an example that looks for certain HTML tags so it's clear that /someregex/.test() returns a boolean:

if(/(span|h[0-6]|li|a)/i.test("h3")) alert('true');

please try this flower:

/^[a-z0-9\_\.\-]{2,20}\@[a-z0-9\_\-]{2,20}\.[a-z]{2,9}$/.test('[email protected]');

true


try

 /^[a-z\d]{5,}$/.test(str)

console.log( /^[a-z\d]{5,}$/.test("abc123") );

console.log( /^[a-z\d]{5,}$/.test("ab12") );


You can try this, it works for me.

 <input type="text"  onchange="CheckValidAmount(this.value)" name="amount" required>

 <script type="text/javascript">
    function CheckValidAmount(amount) {          
       var a = /^(?:\d{1,3}(?:,\d{3})*|\d+)(?:\.\d+)?$/;
       if(amount.match(a)){
           alert("matches");
       }else{
        alert("does not match"); 
       }
    }
</script>

const regExpStr = "^([a-z0-9]{5,})$"
const result = new RegExp(regExpStr, 'g').test("Your string") // here I have used 'g' which means global search
console.log(result) // true if it matched, false if it doesn't