In the provided JavaScript code snippet, we use the nullish coalescing assignment operator (??=) to fill the 'name' variable with the 'defaultName' value if 'name' is null or undefined. This simplifies situations where we used to manually check and write conditional statements, making the code more readable and concise.

example code block;

let name= null;
let defaultName = "john doe";
name ??= defaultName;
console.log(name); // returns "john doe"

// the above statement is equivalent to
if (name === null || name === undefined) {
  name = defaultName;
}