How to Pass a Parameter to a Settimeout() Callback

How can I pass a parameter to a setTimeout() callback?

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);

How do I pass a parameter to a setTimeout() callback?

Since you are missing the parameter in the second form you pass undefined from the second call on, which will essentially result in a timeout of 4ms (which is the browser minimum).

Use a function wrapper, to safely pass the parameters you need:

function blankWord(t){
    console.log('blank!');
    setTimeout(function(){blankWord(t)},t);
}
blankWord(5000);

Passing the parameters as third parameters knocks out older IEs, that's why you should not use this until IE8 is dead.

setTimeout pass parameter in for loop

You don't need .bind(). Either use let or const instead of var...

const $scope = {};

$scope.type = ["st", "ct", "sc", "rm", "bg", "sf", "fl", "sq", "pr", "cr", "vl", "fd"];

for (let i = 0; i < $scope.type.length; i++) {

    setTimeout(function () {

        console.log("i", i);

        // your code

    }, i * 2000);

}

How to pass parameters to setTimeout function

use

var timer = setTimeout(function(){
        countDown(secs)
    },1000);

or

var timer = setTimeout('countDown('  + secs + ')',1000);

In your case the problem was your were using string concatenation with a variable without + sign (my second example) with will cause a syntactical error

when do setTimeOut callback function get its parameters?

Callback function of the setTimeout isn't executed until the call stack is empty and the call stack won't be empty until the execution of your synchronous javascript code completes.

As the last statement overwrites the value of x, when the callback function of setTimeout is invoked, it logs the latest value, i.e. 7.

It seems that you are expecting the callback function of setTimeout to be executed while the for loop is executing BUT that's not how Javascript works.

Once the timer of the setTimeout expires, callback function of the setTimeout is enqueued in the task queue. From the task queue, event loop will push this callback on the call stack BUT the callback function won't be pushed on the call stack until no other javascript code is executing, i.e. the call stack is empty.

It doesn't matters how long it takes for the synchronous script execution to end; no scheduled callback will be executed until the synchronous script execution ends.

Keep in mind that all your code executes on a single thread.

Also note that the number of milliseconds passed to setTimeout is NOT the exact time after which the callback function will be executed; it's the minimum time after which the callback function will be invoked.

SetTimeout function with parameter and without Javascript

setTimout's first parameter is a callback function that will be executed after the timeout. It simply calls the function. It doesn't pass any parameters to it.

The second option is the only one that will work. You'll call createPost(post) and it will push to the array after the timeout that post.

setTimeout function parameters undefined (JS)

You have not passed the parameters to the function callback, when the callback is eventually invoked by the setTimeout the x and y are undefined.

So you see NaN as the output because undefined - undefined is NaN.

setTimeout takes the parameters of the function callback you have passed after the delay argument, in your case after 1000.

Without passing the parameters, the x and y variables is scoped to the function callback. It won't take the values from the outer scope as it is shadowed by the function parameters you have given.

function subtract(x, y) {

    setTimeout(function(x, y) {

      document.write(x - y);

  }, 1000, 1, 1);

}

subtract(1, 1);

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