tree-shaking

Tree Shaking

Setup

Install dependencies

yarn

Run code

yarn dev

Dead Code Elimination

Not used

When the value is defined but not used anywhere.

• not exported and not imported
• not exported and not used in the file/module

Unreachable

Code that's not reachable in the scope.

• Code after a return statement

function test() {
  return 1;
  // this constant is not reachable
  const a = 'not reachable';
}

• Code that is in a unreachable branch (if statement, ternary)

if (true) {
  console.log('hey!');
} else {
  // this console.log is not reachable
  console.log('not reachable');
}

Dead store

When we store data in a variable but this assignment didn't have a real effect because the same variable will be assigned later and the current value is not used for anything.

function test() {
  let a;
  a = 1; // this is a dead store
  a = 2;
  return a;
}