Short answer is : to prevent pollution of the Global (or higher) scope.

IIFE (Immediately Invoked Function Expressions) is the best practice for writing scripts as plug-ins, add-ons, user scripts or whatever scripts are expected to work with other people's scripts. This ensures that any variable you define does not give undesired effects on other scripts.

This is the other way to write IIFE expression. I personally prefer this following method:

void function test() { console.log('boo!'); // expected output: "boo!" }(); 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void

From the example above it is very clear that IIFE can also affect efficiency and performance, because the function that is expected to be run only once will be executed once and then dumped into the void for good. This means that function or method declaration does not remain in memory.

Short answer is : to prevent pollution of the Global (or higher) scope.

IIFE (Immediately Invoked Function Expressions) is the best practice for writing scripts as plug-ins, add-ons, user scripts or whatever scripts are expected to work with other people's scripts. This ensures that any variable you define does not give undesired effects on other scripts.

This is the other way to write IIFE expression. I personally prefer this following method:

void function() { console.log('boo!'); // expected output: "boo!" }(); 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void

From the example above it is very clear that IIFE can also affect efficiency and performance, because the function that is expected to be run only once will be executed once and then dumped into the void for good. This means that function or method declaration does not remain in memory.

Short answer is : to prevent pollution of the Global (or higher) scope.

IIFE (Immediately Invoked Function Expressions) is the best practice for writing scripts as plug-ins, add-ons, user scripts or whatever scripts are expected to work with other people's scripts. This ensures that any variable you define does not give undesired effects on other scripts.

This is the other way to write IIFE block. I personally prefer this following method:

void function test() { console.log('boo!'); // expected output: "boo!" }(); 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void

From the example above it is very clear that IIFE can also affect efficiency and performance, because the function that is expected to be run only once will be executed once and then dumped into the void for good. This means that function or method declaration does not remain in memory.

Short answer is : to prevent pollution of the Global (or higher) scope.

IIFE (Immediately Invoked Function Expressions) is the best practice for writing scripts as plug-ins, add-ons, user scripts or whatever scripts are expected to work with other people's scripts. This ensures that any variable you define does not give undesired effects on other scripts.

This is the other way to write IIFE expression. I personally prefer this following method:

void function test() { console.log('boo!'); // expected output: "boo!" }(); 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/void

From the example above it is very clear that IIFE can also affect efficiency and performance, because the function that is expected to be run only once will be executed once and then dumped into the void for good. This means that function or method declaration does not remain in memory.