javascript SetTimeout 不会延迟函数调用

SetTimeout not delaying a function call

提问by Mark_54

Can somebody please tell me why the setTimeout used in the code below isn't working? It just runs the function straightaway.

有人可以告诉我为什么下面代码中使用的 setTimeout 不起作用吗？它只是直接运行该功能。

function change_txt_font(elem, id, text_fnt){
    current_width = parseInt($('#span_text'+id).css('width')); 
    current_height = parseInt($('#span_text'+id).css('height')); 
    current_font_size = parseInt($("#span_text"+id).css("font-size"));

    parent.document.getElementById(elem+'_f').value=text_fnt;

    $('#span_text'+id).css('font-family',text_fnt);
    $('#'+elem).css('font-family',text_fnt); 
    setTimeout(adjust_for_font(id),2000);
    }

function adjust_for_font(id){
        alert("function")
        alert("id = "+id)
    new_height = parseInt($('#span_text'+id).css('height'));
    new_width = parseInt($('#span_text'+id).css('width'));
    width_ratio = parseFloat(current_width/new_width)
    height_ratio = parseFloat(current_height/new_height)
    new_font_size = current_font_size * Math.min(width_ratio,height_ratio)
    $("#text"+id).css("font-size", (parseFloat(new_font_size) - 1) + "px");
    $("#span_text"+id).css("font-size", (parseFloat(new_font_size) - 1) + "px");
    document.getElementById("form_front_text"+id).submit();
}document.getElementById("form_front_text"+id).submit();
}

Any help appreciated.

任何帮助表示赞赏。

回答by JaredPar

The problem is this line

问题是这条线

setTimeout(adjust_for_font(id),2000);

This doesn't schedule the invoking of adjust_for_font(id)but instead invokes the function directly and schedules the return value. To schedule the invocation of the function wrap the call in a lambda

这不会调度调用，adjust_for_font(id)而是直接调用函数并调度返回值。要安排函数的调用，请将调用包装在 lambda 中

setTimeout(function() { adjust_for_font(id); },2000);

回答by Francis Lewis

By not putting quotes around your function, the function will process immediately, setTimeout will run (but won't process a function) and you're left wondering what on earth happened.

通过不在您的函数周围加上引号，该函数将立即处理，setTimeout 将运行（但不会处理函数），您会想知道到底发生了什么。

setTimeout is designed to run like this:

setTimeout 被设计成这样运行：

setTimeout('adjust_for_font',2000);

Or a using an anonymous function in the callback is another option:

或者在回调中使用匿名函数是另一种选择：

setTimeout(function(){adjust_for_font(id);}, 2000);

回答by Michael Robinson

Change

改变

setTimeout(adjust_for_font(id),2000);

to

到

setTimeout("adjust_for_font(id)",2000);

回答by osahyoun

This should do the trick:

这应该可以解决问题：

setTimeout(adjust_for_font, 2000, id);

I am passing the function name, to be executed when 2000 milliseconds have passed. In your code, you are passing the result of adjust_for_font. The brackets after the function name cause it to be executed as soon as it is parsed (immediately).

我正在传递函数名称，在 2000 毫秒过去后执行。在您的代码中，您传递的是 adjust_for_font 的结果。函数名后面的括号使其在解析后立即执行（立即）。

回答by T. Stone

The way you have it written, it's as if the output of adjust_for_font(id)is the input to the first parameter of setTimeout. The first parameter should be the function, not the result of the function. Try this instead...

按照您的编写方式，就好像 的输出adjust_for_font(id)是 的第一个参数的输入setTimeout。第一个参数应该是函数，而不是函数的结果。试试这个...

setTimeout(function() {
    adjust_for_font(id);
},2000);

回答by Hiran

The SetTimeout syntax is setTimeout(function,milliseconds,param1,param2,...)

SetTimeout 语法是 setTimeout(function,milliseconds,param1,param2,...)

Here "function" means not the calling of the function. It should be the real function.

这里的“函数”不是指函数的调用。它应该是真正的功能。

So you have to change your code to

所以你必须改变你的代码

setTimeout(adjust_for_font,2000,id); (note: The parameter id should pass after the milliseconds parameter)

setTimeout(adjust_for_font,2000,id); （注意：参数id应该在milliseconds参数之后传递）

or alternatively you can set the first parameter as bellow

或者您可以将第一个参数设置如下

setTimeout(function() { adjust_for_font(id); },2000);

setTimeout(function() { adjust_for_font(id); },2000);

回答by Ravi Sankar H

This is from my experiences. Just specifying setTimeout() will cause it to execute upon page load itself, even if it's parent function is not called. making it into a variable like this works..

这是根据我的经验。仅指定 setTimeout() 将导致它在页面加载本身时执行，即使它的父函数没有被调用。把它变成一个像这样的变量..

before

前

function xyz(){
  //do something if needed
  setTimeout(function abc, duration);
  //setTimeout will be executed even before xyz() call
}

after

后

function xyz(){
  //do something if needed
  var t=setTimeout(function abc, duration);
  //this time, setTimeout will be executed upon xyz() call and not upon pageload
}