标签:function topicId 4000 parameter callback setTimeout postinsql
How can I pass a parameter to a setTimeout() callback?
I have some JavaScript code that looks like:
function statechangedPostQuestion()
{
//alert("statechangedPostQuestion");
if (xmlhttp.readyState==4)
{
var topicId = xmlhttp.responseText;
setTimeout("postinsql(topicId)",4000);
}
}
function postinsql(topicId)
{
//alert(topicId);
}
I get an error that topicId
is not defined Everything was working before I used the setTimeout()
function.
I want my postinsql(topicId)
function to be called after some time. What should I do?
回答:
setTimeout(function() {
postinsql(topicId);
}, 4000)
You need to feed an anonymous function as a parameter instead of a string, the latter method shouldn't even work per the ECMAScript specification but browsers are just lenient. This is the proper solution, don't ever rely on passing a string as a 'function' when using setTimeout()
or setInterval()
, it's slower because it has to be evaluated and it just isn't right.
UPDATE:
As Hobblin said in his comments to the question, now you can pass arguments to the function inside setTimeout using Function.prototype.bind()
.
Example:
setTimeout(postinsql.bind(null, topicId), 4000);
标签:function,topicId,4000,parameter,callback,setTimeout,postinsql 来源: https://www.cnblogs.com/chucklu/p/14305716.html
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