How to trim a string to N chars in Javascript? - Stack Overflow

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How can I, using Javascript, make a function that will trim string passed as argument, to a specified length, also passed as argument. For example:

var string = "this is a string";
var length = 6;
var trimmedString = trimFunction(length, string);

// trimmedString should be:
// "this is"

Anyone got ideas? I've heard something about using substring, but didn't quite understand.

How can I, using Javascript, make a function that will trim string passed as argument, to a specified length, also passed as argument. For example:

var string = "this is a string";
var length = 6;
var trimmedString = trimFunction(length, string);

// trimmedString should be:
// "this is"

Anyone got ideas? I've heard something about using substring, but didn't quite understand.

• javascript
• string
• trim

Share Improve this question Follow edited Sep 13, 2018 at 21:04 Lucio 5,36833 gold badges5353 silver badges8181 bronze badges asked Sep 18, 2011 at 18:53 user825286user825286 2

• 3 "this is" = 7 characters, did you intend that ? – aziz punjani Commented Sep 18, 2011 at 18:57
• As said in the question, I'm not too sure how to use substring to do this. Could you please give me an example? I'll accept is an answer of course, if it works ;) @Interstellar_Coder oops, typo! – user825286 Commented Sep 18, 2011 at 18:58

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12 Answers 12

Sorted by: Reset to default 650

Why not just use substring... string.substring(0, 7); The first argument (0) is the starting point. The second argument (7) is the ending point (exclusive). More info here.

var string = "this is a string";
var length = 7;
var trimmedString = string.substring(0, length);

Copying Will's comment into an answer, because I found it useful:

var string = "this is a string";
var length = 20;
var trimmedString = string.length > length ? 
                    string.substring(0, length - 3) + "..." : 
                    string;

Thanks Will.

And a jsfiddle for anyone who cares https://jsfiddle.net/t354gw7e/ :)

I suggest to use an extension for code neatness. Note that extending an internal object prototype could potentially mess with libraries that depend on them.

String.prototype.trimEllip = function (length) {
  return this.length > length ? this.substring(0, length) + "..." : this;
}

And use it like:

var stringObject= 'this is a verrrryyyyyyyyyyyyyyyyyyyyyyyyyyyyylllooooooooooooonggggggggggggsssssssssssssttttttttttrrrrrrrrriiiiiiiiiiinnnnnnnnnnnnggggggggg';
stringObject.trimEllip(25)

Prefer String.prototype.slice over the String.prototype.substring method (in substring, for some cases it gives a different result than what you expect).

Trim the string from LEFT to RIGHT:

const str = "123456789";
result = str.slice(0,5);     // "12345", extracts first 5 characters
result = str.substring(0,5); // "12345"

startIndex > endIndex:

result = str.slice(5,0);     // "", empty string
result = str.substring(5,0); // "12345" , swaps start & end indexes => str.substring(0,5)

Trim the string from RIGHT to LEFT: (-ve start index)

result = str.slice(-3);                 // "789", extracts last 3 characters
result = str.substring(-3);             // "123456789" , -ve becomes 0 => str.substring(0)
result = str.substring(str.length - 3); // "789"

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/substr

From link:

string.substr(start[, length])

    let trimString = function (string, length) {
      return string.length > length ? 
             string.substring(0, length) + '...' :
             string;
    };

Use Case,

let string = 'How to trim a string to N chars in Javascript';

trimString(string, 20);

//How to trim a string...

Little late... I had to respond. This is the simplest way.

// JavaScript
function fixedSize_JS(value, size) {
  return value.padEnd(size).substring(0, size);
}

// JavaScript (Alt)
var fixedSize_JSAlt = function(value, size) {
  return value.padEnd(size).substring(0, size);
}

// Prototype (preferred)
String.prototype.fixedSize = function(size) {
  return this.padEnd(size).substring(0, size);
}

// Overloaded Prototype
function fixedSize(value, size) {
  return value.fixedSize(size);
}

// usage
console.log('Old school JS -> "' + fixedSize_JS('test (30 characters)', 30) + '"');
console.log('Semi-Old school JS -> "' + fixedSize_JSAlt('test (10 characters)', 10) + '"');
console.log('Prototypes (Preferred) -> "' + 'test (25 characters)'.fixedSize(25) + '"');
console.log('Overloaded Prototype (Legacy support) -> "' + fixedSize('test (15 characters)', 15) + '"');

Step by step. .padEnd - Guarentees the length of the string

"The padEnd() method pads the current string with a given string (repeated, if needed) so that the resulting string reaches a given length. The padding is applied from the end (right) of the current string. The source for this interactive example is stored in a GitHub repository." source: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

.substring - limits to the length you need

If you choose to add ellipses, append them to the output.

I gave 4 examples of common JavaScript usages. I highly recommend using the String prototype with Overloading for legacy support. It makes it much easier to implement and change later.

Just another suggestion, removing any trailing white-space

limitStrLength = (text, max_length) => {
    if(text.length > max_length - 3){
        return text.substring(0, max_length).trimEnd() + "..."
    }
    else{
        return text
    }

There are several ways to do achieve this

let description = "your test description your test description your test description";
let finalDesc = shortMe(description, length);

function finalDesc(str, length){

// return str.slice(0,length);

// return str.substr(0, length);

// return str.substring(0, length);

}

You can also modify this function to get in between strings as well.

Here is my solution, which includes trimming white space too.

const trimToN = (text, maxLength, dotCount) => {
  let modText = text.trim();

  if (modText.length > maxLength) {
    modText = text.substring(0, maxLength - dotCount);
    modText = modText.padEnd(maxLength, ".");

    return modText;
  }

  return text;
};

trimToN('Javascript', 6, 2) will return "Java.."

Solution is CSS

If you want to display for example product name, shortened to some length, you can use pure css to do that. I didnt know about it until I started using tailwindcss. Someone will maybe found it helpful, even if its posted in JavaScript question.

-webkit-line-clamp: 3 tells how many lines of text should be in h1 tag. If text is longer, three dots being displayed after last word on last text line.

Browsers support is fine, except IE.

h1 {
max-width: 500px;
overflow: hidden;
display: -webkit-box;
-webkit-box-orient: vertical;
-webkit-line-clamp: 3;
}

<h1>
Germany, Sachsen-Weimar-Eisenach. Wilhelm, (1641-1662). 1/24 Taler 1655, Weimar, auf den Schloßbau zu Weimar. aaaaaaaa aaaaaaa aaaaaaaaa 
</h1>

I think that you should use this code :-)

    // sample string
            const param= "Hi you know anybody like pizaa";

         // You can change limit parameter(up to you)
         const checkTitle = (str, limit = 17) => {
      var newTitle = [];
      if (param.length >= limit) {
        param.split(" ").reduce((acc, cur) => {
          if (acc + cur.length <= limit) {
            newTitle.push(cur);
          }
          return acc + cur.length;
        }, 0);
        return `${newTitle.join(" ")} ...`;
      }
      return param;
    };
    console.log(checkTitle(str));

// result : Hi you know anybody ...

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