How to find a number in a string using JavaScript?

Posted on

How to find a number in a string using JavaScript? – Even if we have a good project plan and a logical concept, we will spend the majority of our time correcting errors abaout javascript and regex. Furthermore, our application can run without obvious errors with JavaScript, we must use various ways to ensure that everything is operating properly. In general, there are two types of errors that you’ll encounter while doing something wrong in code: Syntax Errors and Logic Errors. To make bug fixing easier, every JavaScript error is captured with a full stack trace and the specific line of source code marked. To assist you in resolving the JavaScript error, look at the discuss below to fix problem about How to find a number in a string using JavaScript?.

Problem :

Suppose I have a string like – “you can enter maximum 500 choices”.
I need to extract 500 from the string.

The main problem is the String may vary like “you can enter maximum 12500 choices”.
So how to get the integer part?

Solution :

Use a regular expression.

var r = /d+/;
var s = "you can enter maximum 500 choices";
alert (s.match(r));

The expression d+ means “one or more digits”. Regular expressions by default are greedy meaning they’ll grab as much as they can. Also, this:

var r = /d+/;

is equivalent to:

var r = new RegExp("d+");

See the details for the RegExp object.

The above will grab the first group of digits. You can loop through and find all matches too:

var r = /d+/g;
var s = "you can enter 333 maximum 500 choices";
var m;
while ((m = r.exec(s)) != null) {
  alert(m[0]);
}

The g (global) flag is key for this loop to work.

var regex = /d+/g;
var string = "you can enter maximum 500 choices";
var matches = string.match(regex);  // creates array from matches

document.write(matches);


References:

‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ regular-expressions.info/javascript.html (archive)

‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ ‌‌ developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp (archive)

var str = "you can enter maximum 500 choices";
str = str.replace(/[^0-9]/g, "");
console.log(str); // "500"

I like @jesterjunk answer,
however, a number is not always just digits. Consider those valid numbers:
“123.5, 123,567.789, 12233234+E12”

So I just updated the regular expression:

var regex = /[d|,|.|e|E|+]+/g;

var string = "you can enter maximum 5,123.6 choices";
var matches = string.match(regex);  // creates array from matches

document.write(matches); //5,123.6

var regex = /d+/g;
var string = "you can enter 30%-20% maximum 500 choices";
var matches = string.match(regex);  // creates array from matches

document.write(matches);

You can also try this :

var string = "border-radius:10px 20px 30px 40px";
var numbers = string.match(/d+/g).map(Number);
console.log(numbers)

I thought I’d add my take on this since I’m only interested in the first integer I boiled it down to this:

let errorStringWithNumbers = "error: 404 (not found)";        
let errorNumber = parseInt(errorStringWithNumbers.toString().match(/d+/g)[0]);

.toString() is added only if you get the “string” from an fetch error. If not, then you can remove it from the line.

// stringValue can be anything in which present any number
`const stringValue = 'last_15_days';
// /d+/g is regex which is used for matching number in string
// match helps to find result according to regex from string and return match value
 const result = stringValue.match(/d+/g);
 console.log(result);`

output will be 15

If You want to learn more about regex here are some links:

https://www.w3schools.com/jsref/jsref_obj_regexp.asp

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

https://www.tutorialspoint.com/javascript/javascript_regexp_object.htm

Now this is very easy to do using the ‘replace’ method and ‘regexp’. For example:

findNumber = str => {
  return +(str.replace(/D+/g, ''));
}

console.log(findNumber("you can enter maximum 500 choices"));
console.log(findNumber("you can enter maximum 12500 choices"));

Leave a Reply

Your email address will not be published. Required fields are marked *