freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/basic-algorithm-scripting/truncate-a-string/index.md

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Truncate a String

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Problem Explanation:

We need to reduce the length of the string or truncate it if it is longer than the given maximum length specified and add ... to the end. If it is not that long then we keep it as is.

Relevant Links

• String.prototype.slice()

Hint: 1

Strings are immutable in JavaScript so we will need a new variable to store the truncated string.

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Hint: 2

You will need to use the slice() method and specify where to start and where to stop.

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Spoiler Alert!

Solution ahead!

Basic Code Solution:

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

Run Code

Code Explanation:

• We start off with a simple if statement to determine one of two outcomes...
• If our string length is greater than the num we want to truncate it, we return a slice of our string starting at character 0, and ending at num. We then append our '...' to the end of the string.
• However, if above situation is not true, it means our string length is less than our truncation num. Therefore, we can just return the string.

Advanced Code Solution:

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

Run Code

Code Explanation:

• This solution is very similar to basic solution. To determine the new string, we use a ternary operator. In our ternary operation, if str.length is larger than num, we return a new string which is slice of our string starting at character 0, and ending at num and the '...' is appended to the end of our new string. If str.length is less than or equal to num, we return the string without any truncation.

• NOTE In order to understand the above code, you need to understand how a Ternary Operator works. The Ternary Operator is frequently used as a shortcut for the if statement and follows this format: condition ? expr1 : expr2. If the condition evaluates to true, the operator returns the value of expr1. Otherwise, it returns the value of expr2.

Relevant Links

• Conditional (ternary) Operator
• String.prototype.slice()

NOTES FOR CONTRIBUTIONS:

• DO NOT add solutions that are similar to any existing solutions. If you think it is similar but better, then try to merge (or replace) the existing similar solution.
• Add an explanation of your solution.
• Categorize the solution in one of the following categories — Basic, Intermediate and Advanced.