Explain equality in JavaScript

JavaScript has both strict and type–converting comparisons:

• Strict comparison (e.g., ===) checks for value equality without allowing coercion
• Abstract comparison (e.g. ==) checks for value equality with coercion allowed

 let a = "42"; 
 let b = 42; 
 
 a == b; // true 
 a === b; // false 
       

Some simple equalityrules:

• If either value (aka side) in a comparison could be the true or false value, avoid == and use ===.
• If either value in a comparison could be of these specific values (0, "", or [] — empty array), avoid == and use ===.
• In all other cases, you’re safe to use ==. Not only is it safe, but in many cases it simplifies your code in a way that improves readability.