javascript function works without argument,

Question

function change_tag(url){
  $('.filter_button_confirm').unbind('click').on('click', function(){
    ...
    console.log(url);

    $.ajax({
      url: url,
      type: 'POST',
      data: {
        ...
      },
      beforeSend: function(){
        ...
      }
    })
      .done(function(data){
        ...
      })
  });
};

When I call the function with argument change_tag('/some_url/') of course it works.

But, change_tag() also works perfectly.

It brings data from the url that I set in the past.

console.log(url) shows 'undefined' so I don't know how it knows the url.

What do you want the solution to be? Should the code throw an error if no url is given? — James Monger
– James Monger, Commented Dec 21, 2016 at 14:45
What if you rename your parameter 'url', to check if you are not using a global variable ? — Fabien
– Fabien, Commented Dec 21, 2016 at 14:46

James Monger · Accepted Answer · 2016-12-21 15:09:08Z

9

Since you're not passing in a parameter to the function, url is undefined and so the ajax call gets called with url: undefined. This is the same as not providing an url, and makes it post to the url you're currently on.

For more info you can check the jQuery page: http://api.jquery.com/jquery.ajax/

edited Dec 21, 2016 at 15:09

James Monger

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answered Dec 21, 2016 at 14:47

Robin Dorbell

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2 Comments

James Monger Over a year ago

Calling change_tag() actually calls change_tag with url as undefined, not null.

j08691 Over a year ago

But the OP says that the console log shows undefined for the URL and adds that "It brings data from the url that I set in the past.", not the current URL

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