Checking progressive array - JavaScript

JavascriptWeb DevelopmentFront End TechnologyObject Oriented Programming

We are required to write a JavaScript function that takes in an array of strings, ordered by ascending length.

The function should return true if, for each pair of consecutive strings, the second string can be formed from the first by adding a single letter either at the beginning or end.

For example: If the array is given by −

const arr = ["c", "ca", "can", "acan", "acane", "dacane"];

Then our function should return true.


Following is the code −

const arr = ["c", "ca", "can", "acan", "acane", "dacane"];
const isProgressive = arr => {
   for(let i = 0; i < arr.length-1; i++){
      const nextLength = arr[i+1].length;
      if(arr[i+1] === arr[i+1][0] + arr[i] || arr[i+1] === arr[i] +
      arr[i+1][nextLength-1] ){
      return false;
   return true;


Following is the output in the console −

Published on 18-Sep-2020 12:37:43