A simple analysis on the problem of solving variable change caused by JavaScript asynchronous execution function _javascript skills

On the problem of solving the variable change caused by JavaScript asynchronous execution function

for (Var i=0;i<3;i++)
{
   settimeout (function () {
     console.log (i)
  },0);
}

Console output:
3
3
3

This is because the for loop is executed when execution is done each time it is 3 instead of 1-2-3. Then we can use the immediate execution function to create a variable pair for Each loop for the timer call to solve the problem

for (var i = 0; i < 3; i++) {
      settimeout (
      function () {
        var _i = i;
        return function () {
          console.log (_i)
        };
      }) (),
     0);
    }

Console output:
1
2
3

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