Truncate a String in Javascript

Question

I'm trying to accomplish the following :

Truncate a string (first argument) if it is longer than the given maximum string length (second argument). Return the truncated string with a ... ending.

Note that inserting the three dots to the end will add to the string length.

However, if the given maximum string length num is less than or equal to 3, then the addition of the three dots does not add to the string length in determining the truncated string.

The code I have will only pass test if my num >2, otherwise it fails.

function truncateString(str, num) {
  // Clear out that junk in your trunk
  var trunString = "";
  if (str.length > num) {
  trunString = str.slice(0, (num -3)) + "...";
    return trunString;
  }
  return str;
}

truncateString("A-", 1);

Found a solution for this:

var trunString = "";
  if (str.length > num && num >= 4 ) {
  trunString = str.slice(0, (num - 3)) + "...";
    return trunString;
     }
  else if (str.length > num && num <= 3) {
    trunString = str.slice(0, (num)) + "...";
    return trunString;
  }

Note: Instead of 3 dots (3 characters), maybe you can use the ellipsis … character itself (single character). — techfoobar
– techfoobar, Commented Apr 12, 2016 at 10:44
Or consider those 3 characters while manipulating..Like jsfiddle.net/rayon_1990/w7to3g5p — Rayon
– Rayon, Commented Apr 12, 2016 at 10:45
It will as you are subtracting 3 from your num. If it is 2 or smaller then 2 will produce either 0 or negative and your slice won't work on negative numbers — LearningPhase
– LearningPhase, Commented Apr 12, 2016 at 10:45
the expected output as per the instructions i included in the question is that you must truncate the string and add '...' to the end. without the -3 you would not be accounting for the three dots... — victoria
– victoria, Commented Apr 12, 2016 at 10:54

Nina Scholz · Accepted Answer · 2016-06-20 17:16:11Z

2

You could use a conditional (ternary) operator ?:

function truncateString(str, num) {
    return str.length > num ?
        str.slice(0, num > 3 ? num - 3 : num) + "..." :
        str;
}

console.log(truncateString("Abcdefghijk", 5));
console.log(truncateString("A-", 1));
console.log(truncateString("Alpha", 5));
console.log(truncateString("Beta", 5));
console.log(truncateString("Epsilon", 3));

edited Jun 20, 2016 at 17:16

answered Apr 12, 2016 at 11:00

Nina Scholz

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4 Comments

Yogi Over a year ago

Up voted as your solutions are always elegant code. Yet, the question is a bit unclear. It seems OP wants to always add "..." to the output and allow length > n when n < 3.

victoria Over a year ago

If you run this code it does not work. Alpha and Beta for not have ellipses.

Nina Scholz Over a year ago

should 'Alpha' have dots like 'Al...' and 'Beta' become 'Be...' or 'B...'?

Ievgen S. Over a year ago

nice suggestion. Actually, there is no need to pass the second ternary operator. It will work also with one pair of conditions str.length > num ? str.slice(0, num) + '...' : str;

MarcoS · Accepted Answer · 2016-04-12 12:11:46Z

0

function truncateString(str, num) {
  // clear out that junk in your trunk
  var trunString = '';
  if (str.length && str.length > num) {
    trunString = str.slice(0, num - 1) + '&hellip;';
    return trunString;
  }
  return str;
}

truncateString("A-", 1);

P.S.: read also @techfoobar comment, using &hellip HTML entity will help...

edited Apr 12, 2016 at 12:11

answered Apr 12, 2016 at 10:47

MarcoS

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1 Comment

MarcoS Over a year ago

My answer assumes the string length is the number of rendered chars, ("…".length === 1), and not the lenght of the string in javascript. Hope it fills your requirements...

ZhaoWeihao · Accepted Answer · 2017-05-24 09:41:47Z

-1

This is my solution, hoping to help you

   function truncate(str, num) {
      // Clear out that junk in your trunk
      var newStr;
      if(num>3&&num<str.length){
        newStr=str.slice(0,num-3)+"...";
      }else if(num>=str.length){
        newStr=str;
      }else{
        newStr=str.slice(0,num)+"...";
      }
      return newStr;
    }

    truncate("A-tisket a-tasket A green and yellow basket", "A-tisket a-tasket A green and yellow basket".length);

edited May 24, 2017 at 9:41

answered May 24, 2017 at 8:50

ZhaoWeihao

12 bronze badges

1 Comment

Satan Pandeya Over a year ago

Add some explanation of your answer rather than posting the code only.

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