why settimeout not delay the function execution?

问题

function tryToDownload(url)
{

       oIFrm = document.getElementById('myIFrm');
       oIFrm.src = url;
      // alert(url);
      // url=escape(url);

      setTimeout(deletefile(url), 25000); 
}

following is deletfile function

function deletefile(url){

$.ajax({
    type:'post',
    url: "<%= addToDoDeleteDownloadFile %>",
    data:{filename:url},
    type : "GET",
    timeout : 20000,
    dataType : "text",
    success : function(data) {
        alert("success");

    }
    });
}

above is my jQuery and i m calling one function at the end after 25 second,but some how it's not delaying the deletefile(url) function and execute just after.So what should be the problem?

回答1:

In this line you are calling your function and pass its result to setTimeout().

setTimeout(deletefile(url), 25000);

If you want to delay the execution, add a wrapper function:

setTimeout( function(){ deletefile(url); }, 25000);

EDIT

An alternative proposed by @Petah:

setTimeout(deletefile, 25000, url);

All parameters passed to setTimeout() after the delay, will be passed to the function at execution. So in this case, you pass the reference to the function, the delay and then the parameter to the function in that order!

Note that according to MDN this way of passing parameters wont work in IE before IE9.

回答2:

That's because you are calling the function, and using the return value in the setTimeout call. Wrap it in an anonymous function so that it's called by setTimeout:

function tryToDownload(url) {

    oIFrm = document.getElementById('myIFrm');
    oIFrm.src = url;
   // alert(url);
   // url=escape(url);

   setTimeout(function() { deletefile(url); }, 25000);

}

来源：https://stackoverflow.com/questions/14001795/why-settimeout-not-delay-the-function-execution

标签

javascript

jquery

ajax

liferay

settimeout