Check whether a string matches a regex in JS

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.

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));

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');

Remember to indicate ^ for beginning of the string and $ for the end, if you want to test the exact match of entire string.

Example:

/[a-z]+/.test('aaa111'); // true
/^[a-z]+$/.test('aaa111'); // false

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

try

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

console.log( /^[a-z\d]{5,}$/.test("abc123") ); console.log( /^[a-z\d]{5,}$/.test("ab12") );

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]

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>

please try this flower:

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

true

If you don't want ^ and $ around the regex (I had such a usecase) you can do something like

let reg = /[a-zA-Z0-9]+/g
let txt = "hello"
let matches = reg.exec(txt)[0] == txt
console.log(`It ${matches ? "does" : "doesn't"} match`)

Update/Add

If the query string does not present in the URL then the below solution will work to add the param in the URL, if it already exists then it will update.

function updateUrlParameter(url, param, value) {
  var regex = new RegExp("(?<=[?|&])(" + param + "=)[^&]+", "i");
  if (regex.test(url)) {
    return url.replace(regex, param + "=" + value);
  } else {
    if (window.location.search) {
      return `${url}&${param}=${value}`;
    }else{
      return `${url}?${param}=${value}`;
    }
  }
}