I have a textarea like this:

<textarea>
this is a test [1] also this [2] is a test
and again [3] this is a test
</textarea>

Now I need to get the biggest number which is in []. In this case I need to get 3. How can I do that?

I have a textarea like this:

<textarea>
this is a test [1] also this [2] is a test
and again [3] this is a test
</textarea>

Now I need to get the biggest number which is in []. In this case I need to get 3. How can I do that?

• javascript
• jquery
• regex

• get the value of the textarea in a string variable, extract the values in [] using a regex, parse them to numbers and then sort them and get the highest value. – Roco CTZ Commented Jan 20, 2016 at 23:30

4 Answers 4

You could do:

var result = Math.max.apply(Math, textarea.value.match(/\d+/g).map(Number));

Breaking it up:

textarea.value.match(/\d+/g)

Gets you an array of numbers as strings.

.map(Number)

Maps each entry of the array from a string to a number.

Math.max.apply

Calls Math.max with this as Math and as parameters the mapped array.

Edit: I didn't realize what you needed had to be in between brackets. You'll need to use a capture group for that and it's a little bit more plicated now.

var reg = /\[(\d+)\]/g, numberStrings = [ ], match;
while((match = reg.exec(textarea.value)) !== null){
    numberStrings.push(match[1]);
}

var result = Math.max.apply(Math, numberStrings.map(Number));

It's a little bit more tricky to get the array of strings with the numbers.

Another alternative, without using a capture group:

var numbersInBrackets = textarea.value.match(/\[\d+\]/g);
var numbers = numbersInBrackets.map(function(x) {
    return Number(x.substring(1, x.length - 1));
});
var result = Math.max.apply(Math, numbers);

Same idea as MinusFour's solution. Uses jQuery but could easily be done without.

var content = $('textarea').val();
var contentArr = content.split(' ');
var nums = [];

for (var i = 0; i < contentArr.length; i++) {
  var txt = contentArr[i];
    if (txt.match(/[\d]/)) {
    nums.push(Number(txt.slice(1,-1)));
  }
}

// Max number is Math.max.apply(null, nums)

Full working JSFiddle.

You need to perform 2 actions:

• Get all the [(numbers)] with \[(\d+)] regex
• Get the max value from the resulting array (see this post)

Array.max = function( array ){
    return Math.max.apply( Math, array );
};
var re = /\[(\d+)]/g;
var str = 'this is a test [1] also this [2] is a test\nand again [3] this is a test';
var numbers = [] 
while ((m = re.exec(str)) !== null) {
  numbers.push(Number(m[1]));
}
document.write(Array.max(numbers));

Use this function to find the biggest [number] in any string :

var biggestNumber = function(str) {
    var pattern = /\[([0-9]+)\]/g, match, biggest = 0;

    while ((match = pattern.exec(str)) !== null) {
        if (match.index === pattern.lastIndex) {
            pattern.lastIndex++;
        }
        match[1] = parseInt(match[1]);
        if(biggest < match[1]) {
            biggest = match[1];
        }
    }
    return biggest;
}

DEMO

The following demo calculates the biggest number in your textarea every time you click the button.

It allows you to play around with the textarea and re-test the function with a different text.

var biggestNumber = function(str) {
    var pattern = /\[([0-9]+)\]/g, match, biggest = 0;

    while ((match = pattern.exec(str)) !== null) {
        if (match.index === pattern.lastIndex) {
            pattern.lastIndex++;
        }
        match[1] = parseInt(match[1]);
        if(biggest < match[1]) {
            biggest = match[1];
        }
    }
    return biggest;
}

document.getElementById("myButton").addEventListener("click", function() {
    alert(biggestNumber(document.getElementById("myTextArea").value));
});

<div>
    <textarea rows="4" cols="50" id="myTextArea">
this is a test [1] also this [2] is a test
and again [3] this is a test
    </textarea>
</div>

<div>
   <button id="myButton">Try me</button>
</div>

See also this Fiddle!