loadsh防抖节流源码解读

debounce 源码解析

var isObject = require('./isObject'),
    now = require('./now'),
    toNumber = require('./toNumber');

/** Error message constants. */
var FUNC_ERROR_TEXT = 'Expected a function';

/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeMax = Math.max,
    nativeMin = Math.min;

/**
 * Creates a debounced function that delays invoking `func` until after `wait`
 * milliseconds have elapsed since the last time the debounced function was
 * invoked. The debounced function comes with a `cancel` method to cancel
 * delayed `func` invocations and a `flush` method to immediately invoke them.
 * Provide `options` to indicate whether `func` should be invoked on the
 * leading and/or trailing edge of the `wait` timeout. The `func` is invoked
 * with the last arguments provided to the debounced function. Subsequent
 * calls to the debounced function return the result of the last `func`
 * invocation.
 *
 * **Note:** If `leading` and `trailing` options are `true`, `func` is
 * invoked on the trailing edge of the timeout only if the debounced function
 * is invoked more than once during the `wait` timeout.
 *
 * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
 * until to the next tick, similar to `setTimeout` with a timeout of `0`.
 *
 * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
 * for details over the differences between `_.debounce` and `_.throttle`.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Function
 * @param {Function} func The function to debounce.
 * @param {number} [wait=0] The number of milliseconds to delay.
 * @param {Object} [options={}] The options object.
 * @param {boolean} [options.leading=false]
 *  Specify invoking on the leading edge of the timeout.
 * @param {number} [options.maxWait]
 *  The maximum time `func` is allowed to be delayed before it's invoked.
 * @param {boolean} [options.trailing=true]
 *  Specify invoking on the trailing edge of the timeout.
 * @returns {Function} Returns the new debounced function.
 * @example
 *
 * // Avoid costly calculations while the window size is in flux.
 * jQuery(window).on('resize', _.debounce(calculateLayout, 150));
 *
 * // Invoke `sendMail` when clicked, debouncing subsequent calls.
 * jQuery(element).on('click', _.debounce(sendMail, 300, {
 *   'leading': true,
 *   'trailing': false
 * }));
 *
 * // Ensure `batchLog` is invoked once after 1 second of debounced calls.
 * var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
 * var source = new EventSource('/stream');
 * jQuery(source).on('message', debounced);
 *
 * // Cancel the trailing debounced invocation.
 * jQuery(window).on('popstate', debounced.cancel);
 */
function debounce(func, wait, options) {
  var lastArgs,
      lastThis,
      maxWait,
      result,
      timerId,
      lastCallTime,
      lastInvokeTime = 0,
      leading = false,  //重要的、首要的
      maxing = false,
      trailing = true; // 是否追踪

  if (typeof func != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  wait = toNumber(wait) || 0;
  if (isObject(options)) {
    leading = !!options.leading;
    maxing = 'maxWait' in options;
    maxWait = maxing ? nativeMax(toNumber(options.maxWait) || 0, wait) : maxWait;
    trailing = 'trailing' in options ? !!options.trailing : trailing;
  }

  function invokeFunc(time) {
    var args = lastArgs,
        thisArg = lastThis;

    lastArgs = lastThis = undefined;
    lastInvokeTime = time;
    result = func.apply(thisArg, args);
    return result;
  }

  function leadingEdge(time) {
    // Reset any `maxWait` timer.
    lastInvokeTime = time;
    // Start the timer for the trailing edge.
    timerId = setTimeout(timerExpired, wait);
    // Invoke the leading edge.
    return leading ? invokeFunc(time) : result;
  }

  function remainingWait(time) {
    var timeSinceLastCall = time - lastCallTime,
        timeSinceLastInvoke = time - lastInvokeTime,
        timeWaiting = wait - timeSinceLastCall;

    return maxing
      ? nativeMin(timeWaiting, maxWait - timeSinceLastInvoke)
      : timeWaiting;
  }

  function shouldInvoke(time) {
    var timeSinceLastCall = time - lastCallTime,
        timeSinceLastInvoke = time - lastInvokeTime;

    // Either this is the first call, activity has stopped and we're at the
    // trailing edge, the system time has gone backwards and we're treating
    // it as the trailing edge, or we've hit the `maxWait` limit.
    return (lastCallTime === undefined || (timeSinceLastCall >= wait) ||
      (timeSinceLastCall < 0) || (maxing && timeSinceLastInvoke >= maxWait));
  }

  function timerExpired() {
    var time = now();
    if (shouldInvoke(time)) {
      return trailingEdge(time);
    }
    // Restart the timer.
    timerId = setTimeout(timerExpired, remainingWait(time));
  }

  function trailingEdge(time) {
    timerId = undefined;

    // Only invoke if we have `lastArgs` which means `func` has been
    // debounced at least once.
    if (trailing && lastArgs) {
      return invokeFunc(time);
    }
    lastArgs = lastThis = undefined;
    return result;
  }

  function cancel() {
    if (timerId !== undefined) {
      clearTimeout(timerId);
    }
    lastInvokeTime = 0;
    lastArgs = lastCallTime = lastThis = timerId = undefined;
  }

  function flush() {
    return timerId === undefined ? result : trailingEdge(now());
  }

  function debounced() {
    var time = now(),
        isInvoking = shouldInvoke(time);

    lastArgs = arguments;
    lastThis = this;
    lastCallTime = time;

    if (isInvoking) {
      if (timerId === undefined) {
        return leadingEdge(lastCallTime);
      }
      if (maxing) {
        // Handle invocations in a tight loop.
        timerId = setTimeout(timerExpired, wait);
        return invokeFunc(lastCallTime);
      }
    }
    if (timerId === undefined) {
      timerId = setTimeout(timerExpired, wait);
    }
    return result;
  }
  debounced.cancel = cancel;
  debounced.flush = flush;
  return debounced;
}

module.exports = debounce;

lodash debounce 用法

_.debounce(func, [wait=0], [options={}])

创建一个 debounced（防抖动）函数，该函数会从上一次被调用后，延迟 wait 毫秒后调用 func 方法。 debounced（防抖动）函数提供一个 cancel 方法取消延迟的函数调用以及 flush 方法立即调用。 可以提供一个 options（选项） 对象决定如何调用 func 方法，options.leading 与|或 options.trailing 决定延迟前后如何触发（是 先调用后等待 还是 先等待后调用）。 func 调用时会传入最后一次提供给 debounced（防抖动）函数 的参数。 后续调用的 debounced（防抖动）函数返回是最后一次 func 调用的结果。

注意: 如果 leading 和 trailing 选项为 true, 则 func 允许 trailing 方式调用的条件为: 在 wait 期间多次调用防抖方法。

如果 wait 为 0 并且 leading 为 false, func调用将被推迟到下一个点，类似setTimeout为0的超时。

参数

  • func (Function): 要防抖动的函数。
  • [wait=0] (number): 需要延迟的毫秒数。
  • [options={}] (Object): 选项对象。
  • [options.leading=false] (boolean): 指定在延迟开始前调用。
  • [options.maxWait] (number): 设置 func 允许被延迟的最大值。
  • [options.trailing=true] (boolean): 指定在延迟结束后调用。
    返回
  • (Function): 返回新的 debounced（防抖动）函数。
// 避免窗口在变动时出现昂贵的计算开销。
jQuery(window).on('resize', _.debounce(calculateLayout, 150));
 
// 当点击时 `sendMail` 随后就被调用。
jQuery(element).on('click', _.debounce(sendMail, 300, {
  'leading': true,
  'trailing': false
}));
 
// 确保 `batchLog` 调用1次之后，1秒内会被触发。
var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
var source = new EventSource('/stream');
jQuery(source).on('message', debounced);
 
// 取消一个 trailing 的防抖动调用
jQuery(window).on('popstate', debounced.cancel);

throttle 源码解析

var debounce = require('./debounce'),
    isObject = require('./isObject');

/** Error message constants. */
var FUNC_ERROR_TEXT = 'Expected a function';

/**
 * Creates a throttled function that only invokes `func` at most once per
 * every `wait` milliseconds. The throttled function comes with a `cancel`
 * method to cancel delayed `func` invocations and a `flush` method to
 * immediately invoke them. Provide `options` to indicate whether `func`
 * should be invoked on the leading and/or trailing edge of the `wait`
 * timeout. The `func` is invoked with the last arguments provided to the
 * throttled function. Subsequent calls to the throttled function return the
 * result of the last `func` invocation.
 *
 * **Note:** If `leading` and `trailing` options are `true`, `func` is
 * invoked on the trailing edge of the timeout only if the throttled function
 * is invoked more than once during the `wait` timeout.
 *
 * If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
 * until to the next tick, similar to `setTimeout` with a timeout of `0`.
 *
 * See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
 * for details over the differences between `_.throttle` and `_.debounce`.
 *
 * @static
 * @memberOf _
 * @since 0.1.0
 * @category Function
 * @param {Function} func The function to throttle.
 * @param {number} [wait=0] The number of milliseconds to throttle invocations to.
 * @param {Object} [options={}] The options object.
 * @param {boolean} [options.leading=true]
 *  Specify invoking on the leading edge of the timeout.
 * @param {boolean} [options.trailing=true]
 *  Specify invoking on the trailing edge of the timeout.
 * @returns {Function} Returns the new throttled function.
 * @example
 *
 * // Avoid excessively updating the position while scrolling.
 * jQuery(window).on('scroll', _.throttle(updatePosition, 100));
 *
 * // Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
 * var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
 * jQuery(element).on('click', throttled);
 *
 * // Cancel the trailing throttled invocation.
 * jQuery(window).on('popstate', throttled.cancel);
 */
function throttle(func, wait, options) {
  var leading = true,
      trailing = true;

  if (typeof func != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  if (isObject(options)) {
    leading = 'leading' in options ? !!options.leading : leading;
    trailing = 'trailing' in options ? !!options.trailing : trailing;
  }
  return debounce(func, wait, {
    'leading': leading,
    'maxWait': wait,
    'trailing': trailing
  });
}

module.exports = throttle;

loadsh和装饰器模式结合使用

引用

import Debounce from 'lodash-decorators/debounce';

@Debounce(400)
  resize() {
    if (!this.node) {
      return;
    }
    const canvasWidth = this.node.parentNode.clientWidth;
    const { data = [], autoLabel = true } = this.props;
    if (!autoLabel) {
      return;
    }
    const minWidth = data.length * 30;
    const { autoHideXLabels } = this.state;

    if (canvasWidth <= minWidth) {
      if (!autoHideXLabels) {
        this.setState({
          autoHideXLabels: true,
        });
      }
    } else if (autoHideXLabels) {
      this.setState({
        autoHideXLabels: false,
      });
    }
  }

lodash-decorators/debounce 源码

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var debounce = require("lodash/debounce");
var factory_1 = require("./factory");
var applicators_1 = require("./applicators");
var decorator = factory_1.DecoratorFactory.createInstanceDecorator(new factory_1.DecoratorConfig(debounce, new applicators_1.PreValueApplicator(), { setter: true }));
/**
 * Creates a debounced function that delays invoking func until after wait milliseconds have elapsed since the last time the debounced function was invoked.
 * The debounced function comes with a cancel method to cancel delayed func invocations and a flush method to immediately invoke them.
 * Provide options to indicate whether func should be invoked on the leading and/or trailing edge of the wait timeout. The func is invoked with the last arguments provided to the debounced function.
 * Subsequent calls to the debounced function return the result of the last func invocation.
 *
 * Note: If leading and trailing options are true, func is invoked on the trailing edge of the timeout only if the debounced function is invoked more than once during the wait timeout.
 *
 * If wait is 0 and leading is false, func invocation is deferred until to the next tick, similar to setTimeout with a timeout of 0.
 *
 * @param {number} [wait=0] The number in milliseconds to delay.
 * @param {DebounceOptions} [options] The options object.
 * @example
 *
 * class MyClass {
 *   value = 100;
 *
 *   @Debounce(10)
 *   add(a) {
 *     this.value += a;
 *   }
 * }
 *
 * const myClass = new MyClass();
 *
 * myClass.add(10);
 * myClass.add(50);
 * myClass.add(20);
 *
 * myClass.value; // => 100;
 *
 * setTimeout(() => {
 *   myClass.value; // => 120;
 * }, 11);
 */
function Debounce(wait, options) {
    return decorator(wait, options);
}
exports.Debounce = Debounce;
exports.debounce = Debounce;
exports.default = decorator;
//# sourceMappingURL=debounce.js.map
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