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JS Function Closures

Counting with a local variable.

// Initiate counter
let counter = 0;

// Function to increment counter
function add() {
  let counter = 0; 
  counter += 1;
}

// Call add() 3 times
add();
add();
add();

// The result is not 3 because you mix up the global and local counter
document.getElementById("demo").innerHTML = "The counter is: " + counter;

• It did not work because we display the global counter instead of the local counter.
• We can remove the global counter and access the local counter by letting the function return it: