CSE 121B: JavaScript Language

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 web docs

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.
   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