freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/regular-expressions/positive-and-negative-lookahead/index.md

title
Positive and Negative Lookahead

Positive and Negative Lookahead

• Remeber to use 2 lookaheads to check the patterns in the string. The first lookahead is very similar to that given in the example - '(?=\w{3,6})' - only the lower-number 3 is too low for our test cases, and an upper-number is completely unneccesarry. This first lookahead is only used to find a string consisting of a certain amount of characters. A second lookahead must be used to check for consecutive numerical values at the end of the string.

• The second lookahead is also similar to that given in the example - (?=\D*\d) - however, this expression too must be modified to pass all test cases. Remember to specify the exact amount of numbers you want to appear at the end of the string.

Solution :

let sampleWord = "astronaut";
let pwRegex = /(?=\w{5,})(?=\D*\d{2})/;
let result = pwRegex.test(sampleWord);