JavaScript: Truncate a string if it is longer than the specified number of characters

JavaScript String: Exercise-16 with Solution

Truncate String with Ellipsis

Write a JavaScript function to truncate a string if it is longer than the specified number of characters. Truncated strings will end with a translatable ellipsis sequence ("…") (by default) or specified characters.

Test Data:
console.log(text_truncate('We are doing JS string exercises.'))
console.log(text_truncate('We are doing JS string exercises.',19))
console.log(text_truncate('We are doing JS string exercises.',15,'!!'))
"We are doing JS string exercises."
"We are doing JS ..."
"We are doing !!"

Sample Solution:

JavaScript Code:

// Define a function named text_truncate that takes three parameters: str (the input string), length (the maximum length of the output string), and ending (the optional ending to append if the string is truncated)
text_truncate = function(str, length, ending) {
    // If the length parameter is not provided, set it to 100 characters
    if (length == null) {
      length = 100;
    }
    // If the ending parameter is not provided, set it to '...'
    if (ending == null) {
      ending = '...';
    }
    // Check if the length of the input string exceeds the specified length
    if (str.length > length) {
      // If yes, truncate the string to length - ending.length characters and append the ending
      return str.substring(0, length - ending.length) + ending;
    } else {
      // If no, return the original string
      return str;
    }
  };
// Test the function with different input strings and output the results to the console
console.log(text_truncate('We are doing JS string exercises.'))
console.log(text_truncate('We are doing JS string exercises.',19))
console.log(text_truncate('We are doing JS string exercises.',15,'!!'))

Output:

We are doing JS string exercises.
We are doing JS ...
We are doing !!

Explanation:

In the exercise above,

• The function "text_truncate()" takes three parameters: 'str' (the input string), 'length' (the maximum length of the output string), and 'ending' (an optional ending to append if the string is truncated).
• Inside the function:
• If the 'length' parameter is not provided, it defaults to 100 characters.
• If the 'ending' parameter is not provided, it defaults to '...'.
• It checks if the length of the input string ('str.length') exceeds the specified maximum length ('length').
• If the input string is longer than the maximum length, it truncates the string to 'length - ending.length' characters and appends the 'ending' string.
• If the input string is not longer than the maximum length, it returns the original input string.

Flowchart:

Live Demo:

See the Pen JavaScript Truncate a string if it is longer than the specified number of characters - string-ex-16 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that truncates a string to a specified length and appends an ellipsis (or custom ending) if truncated.
• Write a JavaScript function that validates the maximum length and returns the original string if it is shorter.
• Write a JavaScript function that allows an optional custom truncation suffix instead of the default ellipsis.
• Write a JavaScript function that handles edge cases like zero or negative truncation length.

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