Question

我正在尝试理解一个chrome扩展，它显示html页面中任何选定元素的xpath。我遇到了这个我无法理解的代码。

'use strict';

// Extension namespace.
var xh = xh || {};

xh.bind = function(object, method) {
  return function() {
    return method.apply(object, arguments);
  };
};
////////////////////////////////////////////////////////////////////////////////
// xh.Bar class definition

xh.Bar = function() {
  this.boundShowBar_ = xh.bind(this, this.showBar_);
  this.boundHandleRequest_ = xh.bind(this, this.handleRequest_);
  this.boundMouseMove_ = xh.bind(this, this.mouseMove_);
  this.boundKeyDown_ = xh.bind(this, this.keyDown_);

  chrome.extension.onMessage.addListener(this.boundHandleRequest_);

  this.barFrame_ = document.createElement('iframe');
  this.barFrame_.src = chrome.extension.getURL('bar.html');
  this.barFrame_.id = 'xh-bar';
  this.barFrame_.className = 'top';
  this.barFrame_.style.height = '0';

  // Temporarily make bar 'hidden' and add it to the DOM. Once the bar's html
  // has loaded, it will send us a message with its height, at which point we'll
  // set this.barHeightInPx_, remove it from the DOM, and make it 'visible'.
  // We'll add it back to the DOM on the first bar request.
  //this.barFrame_.style.visibility = 'hidden';
  document.body.appendChild(this.barFrame_);

  document.addEventListener('keydown', this.boundKeyDown_);
};

xh.Bar.prototype.active_ = false;
xh.Bar.prototype.barFrame_ = null;
xh.Bar.prototype.barHeightInPx_ = 0;
xh.Bar.prototype.currEl_ = null;
xh.Bar.prototype.boundHandleRequest_ = null;
xh.Bar.prototype.boundMouseMove_ = null;
xh.Bar.prototype.boundKeyDown_ = null;

绑定功能究竟在做什么？调用bind时使用的方法未在代码中的任何位置定义。

Answer 1

bind(thisArg : Object, [param1 : Object, [param2 : Object, [...]]]) : Function

返回一个新函数，当调用它时，它将等于thisArg，第一个参数等于param1，第二个参数等于param2等。

我们主要使用Bind（）方法调用具有显式设置的值的函数。换句话说，bind（）允许我们在调用函数或方法时轻松设置将绑定到哪个特定对象。

javascript类中的变量定义

1 个答案: