Simple learning of for statement loop structure in JavaScript

You can directly look at the examples, it's too many to use, it's very simple

(function() {
  for(var i=0, len=; i&lt;len; i++) {
    if (i == 2) {
      // return; // function execution is terminated      // break; // The loop is terminated      continue; // The loop is skipped    };
    ('demo1Arr['+ i +']:' + demo1Arr[i]);
  }
})();

Regarding the for loop, there are some points to pay attention to

i in the for loop still exists in the scope after the loop ends. In order to avoid affecting other variables in the scope, it is isolated by using the function self-execution method ()();
Avoid using for(var i=0; i<; i++){}, such array length is calculated every time, which is less efficient than the above method. You can also place variable declarations in front of for to perform to improve reading
var i = 0, len = ;
for(; i<len; i++) {};

There are several ways to break out of the loop

The return function execution is terminated
break loop is terminated
The continue loop is skipped

Complete example:

&lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
&lt;head&gt;
 &lt;meta charset="UTF-8"&gt;
 &lt;title&gt;Detailed explanation of traversal: for&lt;/title&gt;
 &lt;script src="../script/jquery-2.0."&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
 
&lt;/body&gt;
&lt;script&gt;
 var demo1Arr = ['Javascript', 'Gulp', 'CSS3', 'Grunt', 'jQuery', 'angular'];
 (function() {
 for(var i=0, len=; i&lt;len; i++) {
  if (i == 2) {
  // return; // function execution is terminated  // break; // The loop is terminated  continue; // The loop is skipped  };
  ('demo1Arr['+ i +']:' + demo1Arr[i]);
 }
 })();
&lt;/script&gt;
&lt;/html&gt;