The existence and parameter problems of function in the jquery library of JavaScript _jquery

jQuery function Parameter Pass

Use external variables in the function functions of jquery:

How to obtain I variable for
(i=0;i<3;i++) {
 $.get ("/test.html", function (data) { 
  alert (i)
 });


Use closure:
for (i=0;i<3;i++) {
 (function (index) {
  $.get ("/test.html", function (data) { 
  alert ( Index)
  });
 (i)
}

JavaScript, JQuery detects whether a function exists

The method for detecting whether a function exists in JavaScript is:

if (typeof $form. Validate = = ' function ') {
 console.log (' This function exists ');
} else {
 console.log (' This function does not exist ');
}

For example, you need to detect whether a MD5 method exists:

if (typeof window.md5 = = ' function ') {
 //if pure in this method, the call to
 MD5 (286);
}

To detect if a JQuery method exists, use the following methods:

if (Jquery.isfunction (jQuery.fn.rtFunction)) {
 //If the method exists, invoke
 JQuery (document). Rtfunction ();