简单的油门在js [英] Simple throttle in js

问题描述

我在JS中寻找一个简单的油门。我知道像lodash和下划线这样的库有它，但只有一个函数包含任何这些库都是过度的。

I am looking for a simple throttle in JS. I know libraries like lodash and underscore have it, but only for one function it will be overkill to include any of those libraries.

我还在检查jquery是否有类似的功能 - 找不到。

I was also checking if jquery has a similar function - could not find.

我找到了一个工作油门，这里是代码：

function throttle(fn, threshhold, scope) {
  threshhold || (threshhold = 250);
  var last,
      deferTimer;
  return function () {
    var context = scope || this;

    var now = +new Date,
        args = arguments;
    if (last && now < last + threshhold) {
      // hold on to it
      clearTimeout(deferTimer);
      deferTimer = setTimeout(function () {
        last = now;
        fn.apply(context, args);
      }, threshhold);
    } else {
      last = now;
      fn.apply(context, args);
    }
  };
}

这个问题是：它在节流时间后再次触发该功能完成了。所以我们假设我在按键时每隔10秒发一个油门 - 如果我按下2次按键，它会在10秒钟完成时触发第二次按键。我不想要这种行为。

The problem with this is: it fires the function once more after the throttle time is complete. So let's assume I made a throttle that fires every 10 seconds on keypress - if I do keypress 2 times, it will still fire the second keypress when 10 seconds are completed. I do not want this behavior.

推荐答案

我会使用 underscore.js 或 lodash 源代码，找到这个函数的经过良好测试的版本。

I would use the underscore.js or lodash source code to find a well tested version of this function.

这是下划线代码的略微修改版本，用于删除对下划线的所有引用。 js本人：

Here is the slightly modified version of the underscore code to remove all references to underscore.js himself:

// Returns a function, that, when invoked, will only be triggered at most once
// during a given window of time. Normally, the throttled function will run
// as much as it can, without ever going more than once per `wait` duration;
// but if you'd like to disable the execution on the leading edge, pass
// `{leading: false}`. To disable execution on the trailing edge, ditto.
function throttle(func, wait, options) {
  var context, args, result;
  var timeout = null;
  var previous = 0;
  if (!options) options = {};
  var later = function() {
    previous = options.leading === false ? 0 : Date.now();
    timeout = null;
    result = func.apply(context, args);
    if (!timeout) context = args = null;
  };
  return function() {
    var now = Date.now();
    if (!previous && options.leading === false) previous = now;
    var remaining = wait - (now - previous);
    context = this;
    args = arguments;
    if (remaining <= 0 || remaining > wait) {
      if (timeout) {
        clearTimeout(timeout);
        timeout = null;
      }
      previous = now;
      result = func.apply(context, args);
      if (!timeout) context = args = null;
    } else if (!timeout && options.trailing !== false) {
      timeout = setTimeout(later, remaining);
    }
    return result;
  };
};

请注意，如果您不需要所有支持下划线的选项，则可以简化此代码。

Please note that this code can be simplified if you don't need all the options that underscore support.

编辑1：删除了对下划线的另一个引用，thx到Zettam的评论

Edit 1: Removed another reference to underscore, thx to Zettam's comment

编辑2：添加了关于lodash的建议和可能的代码简化，thx to lolzery wowzery的评论

Edit 2: Added suggestion about lodash and possible code simplification, thx to lolzery wowzery's comment

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