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Javascript closure inside loops – simple practical example
Javascript: closure of loop?

so I would like the results to be 1,2,3 instead of 3,3,3. How do I set the context/scope so that the jobs are using the correctly scoped “i”?

function buildJobs(list) {
  var jobs = [];
  for (var i = 0; i < list.length; i++) {
    var item = list[i];
    jobs.push( function() {alert(item)} );
  }
  return jobs;
}

function testJobs() {
  var jobs = buildJobs([1,2,3]);
  for (var j = 0; j < jobs.length; j++) {
    jobs[j]();
  }
}

Answer 1

Wrap the inner function with a another function that’s immediately executed and receives i as an argument:

function buildJobs(list) {
  var jobs = [];
  for (var i = 0; i < list.length; i++) {
    var item = list[i];
    (function(i) {
      jobs.push( function() {alert(list[i])} );
    })(i);
  }
  return jobs;
}

You’re now closing over the i that is local to the wrapper function, which is a different variable in each iteration. (In your original configuration each inner function was closing over the same variable (whose value was 3 by the time any of the functions ever executed).)