freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/basic-algorithm-scripting/confirm-the-ending/index.md

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Confirm the Ending

Confirm the Ending

🌻 Intermediate Code Solution:

(Declarative approach)

function confirmEnding(str, target) {
  // "Never give up and good luck will find you."
  // -- Falcor
  
  return str.slice(str.length - target.length) === target;
}

confirmEnding("He has to give me a new name", "name");

🚀 Run Code

Code Explanation:

• First we use the slice method copy the string.
• In order to get the last characters in str equivalent to the target's length we use the slice method.
• The first parameter inside the slice method is the starting index and the second parameter would be the ending index.
• For example str.slice(10, 17) would return give me.
• In this case we only include one parameter which it will copy everything from the starting index.
• We substract the length of str and the length of target, that way, we shall get the last remaining characters equivalent to the target's length.
• Finally we compare the return result of slice to target and check if they have the same characters.

Relevant Links

• String.prototype.slice()

Advanced Code Solution:

(using Regular Expression)

function confirmEnding(str, target) {
 // "Never give up and good luck will find you."
 // -- Falcor
 
 let re = new RegExp(target+'$','i');
 
 return re.test(str);
}

console.log(confirmEnding("Bastian", "n"));

Code Explanation:

• We need to make a pattern from the target variable that exists at the end of the string str.
• Since we will use a variable that will change the pattern each time the function is called, we will use the constructor of the regular expression object new RegExp(pattern[, flags]), so we start with: new RegExp(target).
• Then we have to check at the end of the string, so we concatenate to the target variable the $ character to match the end: new RegExp(target+'$').
• We use the flag i to ignore the case of the pattern and we have our completed RegExp: new RegExp(target+'$','i'), or we can ommit the flag entirely.
• Finally, we are using our regular expression with the test method to the given string, to check if the string ends with the pattern and return true or false accordingly.

Relevant Links

• RegExp
• RegExp.prototype.test()