📓NOTES 4.3: Conditionals & Iteration

Table of Contents

Program Flow Control

Branching (Conditionals)

if Statements

Complete steps 7-14 in the following interactive tutorial: 🏗️ JS Construction Site

Comparison Operators

“Truthiness”

When we use if() statements, we are not always going to be able to plug in a variable that already holds the value of true or false. Many times, we must plug in a statement that will be evaluated by JavaScript as true or false.

For example, do you know if the value 0 is true or false?

This is not a philosophy question – JavaScript has an answer. This happens because JavaScript is a weakly typed language. This means that in the context of an if() statement, it will convert other variable values to true or false in order to run the code. This is known as determining the “truthiness” of a value.

This is similar to the legal system! Although it is POSSIBLE that there will be one piece of evidence that makes the “guilty” or “not guilty” sentence obvious, it is also likely that a judge or jury will need to evaluate the evidence and make a decision.

For this analogy, let’s assume a true statement is one that will lead to the conviction of the accused car theft, while a false statement will let him/her walk free.

let evidence = "Fingerprints";
 
if (evidence) {
  convict();
}
 
else {
  release();
}

convict() and release() are made-up functions. In this case, since evidence has a non-zero/non-empty value, the if() statement evaluates to true, so the judge would convict the car thief.

Here’s an interactive diagram of this scenario:

Looping (Iteration)

while Loops

for...in loops

Acknowledgement

Content on this page is adapted from the MDN Web Docs, The Modern JavaScript Tutorial, and CodeAnalogies Blog.