this

问题 var a = 1; var b = { a : 2, c : function () { console.log(this.a); } }; b.c(); // logs 2 (b.c)(); // logs 2 (0, b.c)(); // logs 1 The first is understandable, for "this" is pointed to Object "b". But why does the second one log the same result? I thought "this" should be pointed to the global execution context. And the third one, it seems that the comma operator influences the execution context. 回答1: You really have a nice corner case there! My take on it: the first is straightforward. Just a

问题 The behavior of "this" when function bar is called is baffling me. See the code below. Is there any way to arrange for "this" to be a plain old js object instance when bar is called from a click handler, instead of being the html element? // a class with a method function foo() { this.bar(); // when called here, "this" is the foo instance var barf = this.bar; barf(); // when called here, "this" is the global object // when called from a click, "this" is the html element $("#thing").after($("

问题 There are two ways to reference the instance of a class within that class. For example: class Person { String name; public void setName(String name) { this.name = name; } public void setName2(String name) { Person.this.name = name; } } One uses this.name to reference the object field, but the other uses className.this to reference the object field. What is the difference between these two references? 回答1: In this case, they are the same. The Class.this syntax is useful when you have a non

问题 Here I have a number array. I tried to test if Array.prototype.forEach can be used on array in a different way than the traditional way. In traditional way we pass the THIS argument as second parameter to forEach . Here I used Array.prototype.forEach.call() and for this I used the array as argument to call method. But this indication the window object. Why is that ? number=[1,2,3,4,5]; Array.prototype.forEach.call(number,function(elem){ console.log(this); }); 回答1: Because assuming forEach has

问题 Learning jQuery and I have a couple of questions. I am wondering why this won't work: $('li').html(function(){ return '<em>' + this.text() + '</em>'; }); But this will: $('li').html(function(){ return '<em>' + $(this).text() + '</em>'; }); And also, why is this working: $(document).on('load', alert('done')); But not this: $(document).on('load', function(){alert('done'); }); Thanks, 回答1: this and $(this): In the first example, this is a node element, and since node elements don't have a

问题 This question already has answers here : How to access the correct `this` inside a callback? (10 answers) Closed 3 years ago . When I use react with es6 and jquery's ajax function, I got this.setState() is not a function error. I tried bind this within constructor using this.componentDidmount = this.componentDidmount.bind(this); , but still not working. Can any one help me? Thanks! Here is my code: import React from 'react'; import $ from 'jquery'; class UserGist extends React.Component {

问题 I have a grid with an image being grey, on hover the image get colorize (the image can not be setup as background image for information). When Hover the image, a text appear, on click on this, I have a content which toggle. Here are my two issues: 1 On toggle, only the image of the item have click should be colorize, actually they all get colorize unfortunatly. ( test on the first item of the secodn row) I tried to use $(this).prev without success. ( see the code) //** HERE THE TOGGLE

问题 How do I get the ID associated with the this keyword? I've tried several things from SO pages but here is where I've decided to open the question: $('.anySelector').waypoint(function() { console.log(this); // entire selector's content var thisContent = this; console.log($(thisContent).attr('id')); // undefined }); 回答1: If this really is a DOM Element (which is very probable using jQuery) it is as simple as just accessing the id property of the element. jQuery( '.anySelector' ).waypoint(

问题 I have an abstract class Flight. Flight contains the method schedule() which calls the private method schedule(final Flight f) public void schedule() { schedule(this); } private void schedule(final Flight f) { new Timer().schedule(new TimerTask() { @Override public void run() { f.checkIn(); updateList(); } }, this.getDate()); } Lets now say I have a class SouthWestFlight that extends Flight Flight f = new SouthWestFlight(); //ignore the missing params doesn't matter for example f.schedule();

问题 I thought I understood wel the "this" keyword until I saw this code : <body> <button onclick="go()">clic1</button> <button id="btn">clic2</button> <script> function go() { console.log(this); } var btn = document.getElementById("btn"); btn.onclick = function() { console.log(this) } </script> </body> I have a HTML document with two buttons that do the same thing when clicked :they log the "this" keyword. I'm very surprised they don't show the same result : For the button "clic1" : this = Window