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问题 This question already has answers here : When should I make explicit use of the `this` pointer? (12 answers) Closed 2 years ago . I'm dealing with a large code base that uses the following construct throughout class MyClass { public: void f(int x); private: int x; }; void MyClass::f(int x) { ' ' this->x = x; ' ' } Personally, I'd always used and hence prefer the form class MyClass { public: void f(int x); private: int _x; }; void MyClass::f(int x) { ' ' _x = x; ' ' } The reasons I prefer the

问题 This question already has answers here : When should I make explicit use of the `this` pointer? (12 answers) Closed 2 years ago . I'm dealing with a large code base that uses the following construct throughout class MyClass { public: void f(int x); private: int x; }; void MyClass::f(int x) { ' ' this->x = x; ' ' } Personally, I'd always used and hence prefer the form class MyClass { public: void f(int x); private: int _x; }; void MyClass::f(int x) { ' ' _x = x; ' ' } The reasons I prefer the

问题 This question already has answers here : Self-references in object literals / initializers (23 answers) Closed 3 years ago . I'm trying to calculate a proportional height (while excluding a static height element) from a width that gets passed in via a request (defaults to 560). However, wF.h evaluates to NaN . If I replace this.w with 560 it works, but not when trying to reference the w property of wF . var wF = { w : 560, h : (312 - 42) / (560 / this.w) + 42 }; What gives? I refuse to use

问题 Explanation to why this is not a duplicate: My code is already working, I have included as a comment. The question is why the this context change when I include it to click handler function. I'm attempting a calculator project in React. The goal is to attach onclick handlers to number buttons so the numbers are displayed on the calculator display area. If the handler is written directly to render method it is working, however, if I'm trying from the ComponentDidMount I get an error this

问题 I'm sure there's a simple answer to this, but it's Friday afternoon and I'm tired. :( Not sure how to explain it, so I'll just go ahead and post example code... Here is a simple object: var Bob = { Stuff : '' , init : function() { this.Stuff = arguments[0] } , doSomething : function() { console.log( this.Stuff ); } } And here it is being used: $j = jQuery.noConflict(); $j(document).ready( init ); function init() { Bob.init('hello'); Bob.doSomething(); $j('#MyButton').click( Bob.doSomething );

问题 Can anybody explain to me why A is true and B is false? I would have expected B to be true as well. function MyObject() { }; MyObject.prototype.test = function () { console.log("A", this instanceof MyObject); (function () { console.log("B", this instanceof MyObject); }()); } new MyObject().test(); 回答1: this is special. It refers to the object that the function is being called on behalf of (most commonly via dot syntax). So, in the case of A , the function is being called on behalf of a new

问题 This question already has answers here : Preserving a reference to “this” in JavaScript prototype functions [duplicate] (7 answers) Closed 3 years ago . What is the correct way to preserve a this javascript reference in an event handler stored inside the object's prototype? I'd like to stay away from creating temp vars like '_this' or 'that' and I can't use a framework like jQuery. I saw a lot of people talk about using a 'bind' function but was unsure of how to implement it in my given

问题 Given the following code: public interface Selectable { public void select(); } public class Container implements Selectable { public void select() { ... } public void createAnonymousClass() { Selectable s = new Selectable() { public void select() { //see comment below. } }; } } I want to access Container.select() from within my anonymous class' select() method. However, this.select() would again call the anonymous class' select() method. My suggestion would be: Introduce a field into

问题 I have created a 'control' using jQuery and used jQuery.extend to assist in making it as OO as possible. During the initialisation of my control I wire up various click events like so jQuery('#available input', this.controlDiv).bind('click', this, this.availableCategoryClick); Notice that I am pasing 'this' as the data argument in the bind method. I do this so that I can get at data attached to the control instance rather from the element that fires the click event. This works perfectly,

问题 I was wondering what the 'this' value (or invocation context) is of the forEach callback function. This code doesn't seem to work: var jow = [5, 10, 45, 67]; jow.forEach(function(v, i, a){ this[i] = v + 1; }); alert(jow); Thx for explaining it to me. 回答1: MDN states: array.forEach(callback[, thisArg]) If a thisArg parameter is provided to forEach, it will be used as the this value for each callback invocation as if callback.call(thisArg, element, index, array) was called. If thisArg is