WDD 131: Dynamic Web Fundamentals

Loops and Iteration

Overview

Repeating code is a common task in programming. JavaScript provides several ways to repeat code including for, while, do...while, and for...in statements. Each of these statements has a specific use case and syntax. forEach is a method that can be used on arrays to iterate over each item in the array.

Prepare

• Read: Loops and Iteration - MDN

Check Your Understanding

1. Complete the activities presented in this resource: JavaScript Loops - WDD Learning Modules
2. Given the following variable declarations:

   const DAYS = 6;
   const LIMIT = 30;
   let studentReport = [11, 42, 33, 64, 29, 37, 44];

   • Write a for loop that will iterate through the studentReport array and print to the console the current array value if it is below 30.
   • Repeat the previous programming snippet by using a while loop.
   • Repeat the previous programming snippet by using a forEach loop.
   • Repeat the previous programming snippet by using a for...in loop.
   • Use any type of repetition (looping) statement to dynamically produce the day names (Monday, Tuesday, Wednesday, etc.) of the next number of DAYS from today's date.
   Check Your Understanind - Example Answers

   These answers are certainly not exhaustive.

   
     // for loop
     for (let i = 0; i < studentReport.length; i++) {
       if (studentReport[i] < LIMIT) {
         console.log(studentReport[i]);
       }
     }
   
     // while loop
     let i = 0;
     while (i < studentReport.length) {
       if (studentReport[i] < LIMIT) {
         console.log(studentReport[i]);
       }
       i++;
     }
   
     // forEach loop
     studentReport.forEach(function (item) {
       if (item < LIMIT) {
         console.log(item);
       }
     });
   
     // for...in loop
     for (let i in studentReport) {
       if (studentReport[i] < LIMIT) {
         console.log(studentReport[i]);
       }
     }

   Use this CodePen to guide you in a solution to the last question. This requires you to sift through the example code to find what is applicable.

   CodePen: JavaScript - Get Future Days from Today