Default exports in Javascript - Step-by-Step Execution

Concept Flow - Default exports

Create module file

↓

Write export default statement

↓

Import module in another file

↓

Use imported default export

↓

Run program

This flow shows how a JavaScript module defines a default export, which is then imported and used in another file.

Execution Sample

Javascript

export default function greet() {
  return "Hello!";
}

import greet from './greet.js';
console.log(greet());

This code exports a default function greet and imports it to print a greeting.

Execution Table

Step	Action	Evaluation	Result
1	Define default export function greet	Function greet created	greet is ready to export
2	Export greet as default	Module exports greet as default	Default export set
3	Import default export as greet	greet refers to default export	greet function imported
4	Call greet()	Execute greet function	"Hello!" returned
5	console.log output	Print returned value	Hello! printed to console

💡 Program ends after printing the greeting.

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
greet	undefined	function greet()	function greet()	function greet()

Key Moments - 3 Insights

Why do we not use curly braces when importing a default export?

Because the execution_table row 3 shows the import uses the syntax without braces to get the default export directly.

Can a module have more than one default export?

No, as shown in step 2, only one default export is allowed per module.

What happens if you import a default export with a different name?

The imported name is just a local alias, so you can name it anything, as shown in step 3 where 'greet' is the local name.

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 5?

A undefined printed

B Error thrown

C "Hello!" printed to console

D Nothing printed

💡 Hint

Check the 'Result' column in step 5 of the execution_table.

At which step is the default export set in the module?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column describing export default in the execution_table.

If we change the import name from 'greet' to 'hello', what changes in the variable_tracker?

A The variable name changes to 'hello' but value stays the same

B The function changes behavior

C The import fails

D No change at all

💡 Hint

Variable names in variable_tracker reflect local names after import, see step 3.

Concept Snapshot

Default exports allow a module to export a single value or function.
Use 'export default' to set it.
Import without braces to get the default export.
You can name the import anything you want.
Only one default export per module.

Full Transcript

This visual execution trace shows how JavaScript default exports work. First, a function greet is defined and exported as the default export of a module. Then, in another file, this default export is imported using the syntax without curly braces and assigned to the local name greet. Calling greet() runs the function and returns 'Hello!'. Finally, console.log prints this returned string. The variable tracker shows greet as a function throughout. Key points include that default exports are imported without braces, only one default export is allowed, and the import name is a local alias. The quizzes test understanding of output, export step, and renaming imports.