How to Truncate a String in JavaScript

1. Use substr() Method to Truncate a String in JavaScript
2. Use split() and join() Method to Truncate String in JavaScript

The floor(), ceil(), round(), and trunc() functions deal with numbers or any float numbers, but in the case of the string data type, there is no direct function to truncate or round till a limit.

The common drive introduces the substr() method that cuts a sentence, a.k.a string, up to a limit. This method draws out a substring from the stated string.

We will discuss the ways of using the mentioned JavaScript functions and methods.

Use substr() Method to Truncate a String in JavaScript

The substr() method takes two arguments to function the process.

The first parameter takes the start point (index) from where the truncation will start, and the latter parameter is to set the limit till which index the truncation will stop.

It is to be mentioned that the truncation terminates before the limit parameter. We will examine the line as we follow the instances.

Code Snippet:

function truncate(str, limit) {
  if (str.length > limit) {
    str = str.substr(0, limit);
  } else {
    return str;
  }
  return str;
}
console.log(truncate('Scooby-doo this crap', 10));

Output:

We noticed that the first parameter for the method was 0 while the limit was set to 10. So, the output prints the characters up to the 9th index.

If we only had one parameter for the method, it would infer as the start index and print the string until the end index. For the string we have in the example, if we have substr(10), we will get the outcome (whitespace)this crap.

Use split() and join() Method to Truncate String in JavaScript

The manual way to truncate a string is by splitting a string into an array and getting the expected substring or truncated string. The example shows how a string is split into an array and truncate, join and print.

Code Snippet:

var str = 'I like to move it move it!';
str = str.split('');
var newStr = [];
var limit = 10;
for (var i = 0; i < limit; i++) {
  newStr[i] = str[i];
}
newStr = newStr.join('');
console.log(newStr);

Output:

The str object has a string stored, and we have reinitialized the str to save the array form after applying the spilt() method. We can calculate the array’s length to perform str.length.

After that, we initiated a for loop, setting the counter from the 0 index and ending until the limit value. You can select an index of preference as the start point of truncation.

The next task is to reallocate the str array characters to the newStr array before joining the newStr and printing the console’s result. Our limit was set to index 10, and the last printed character was the 9th index.