javascript closure trap

javascript_closure.js

// What is the result of the following?
for (var i=0; i<10; ++i) {
  setTimeout(function() {
    console.log(i);
  }, 1000);
}


// using IIFE (immediately invoked function) 
// with delay
for (var i=0; i<10; ++i) {
  (function(j) {
     setTimeout(function() {
      console.log(j);
     }, 1000);
  })(i);
}

// without delay
for (var i=0; i<10; ++i) {
  setTimeout((function(i) {
    console.log(i);
  })(i), 1000)
}


// wrap in a function 
for (var i = 0; i < 10; i++) {
  function timer(j) {
       setTimeout(function() {
        console.log(j);
     }, j);
   };
  timer(i); 
}


// ES6, use let instead of var
for (let i=0; i<10; ++i) {
  setTimeout(function() {
    console.log(i);
  }, 1000);
}


// Ref: https://hackernoon.com/how-to-use-javascript-closures-with-confidence-85cd1f841a6b