JavaScript Variable Scope [duplicate]

by

The setTimeout callback functions are executed asynchronously, all the console.log calls you make refer to the same i variable, and at the time they are executed, the for loop has ended and i contains 4.

You could wrap your inner setTimeout call inside a function accepting a parameter in order to store a reference to all the i values that are being iterated, something like this:

setTimeout(function() {
    for (var i = 0; i < 5; i++) {
      (function (j) { // added a closure to store a reference to 'i' values
        setTimeout(function() {
            console.log(j);
        }, j * 200);
      })(i); // automatically call the function and pass the value
    }
}, 200);

Check my answer to the following question for more details:

More Related Contents:

  1. Please explain the use of JavaScript closures in loops [duplicate]
  2. JavaScript variable binding and loop
  3. javascript closure immediate evaluation [duplicate]
  4. How do JavaScript closures work?
  5. JavaScript closure inside loops – simple practical example
  6. Event handlers inside a Javascript loop – need a closure?
  7. var self = this?
  8. JavaScript closures vs. anonymous functions
  9. Is it possible to gain access to the closure of a function?
  10. Access outside variable in loop from Javascript closure [duplicate]
  11. Doesn’t JavaScript support closures with local variables? [duplicate]
  12. What underlies this JavaScript idiom: var self = this?
  13. How does a function in a loop (which returns another function) work? [duplicate]
  14. Javascript closure not working
  15. Is window really global in Javascript?
  16. Closures in a for loop
  17. passing index from for loop to ajax callback function (JavaScript)
  18. JavaScript scope and closure
  19. Javascript closures – variable scope question
  20. Passing values to onclick [duplicate]
  21. Closure in Javascript [duplicate]
  22. How are local variables referenced in closures? [duplicate]
  23. dynamically call local function in javascript
  24. Setting onclick to use current value of variable in loop [duplicate]
  25. Assigning prototype methods *inside* the constructor function – why not?
  26. How do I build a loop in JavaScript? [closed]
  27. javascript – How to make this code work? [duplicate]
  28. Access a variable outside the scope of a Handlebars.js each loop
  29. JavaScript – Map() increment value
  30. Looping over urls to do the same thing

Leave a Comment