IntersectionObserver: "Uncaught TypeError: Cannot read property of undefined" when called onIntersection()

Question

我有以下代码：

var ObjectOne = {
    a : {
        b : 4,
        ...
    }        
    observer : 0,
    ...

    init() { 
        this.a.b = 5;           
        ...
        this.observer = new IntersectionObserver(this.onIntersection, ...);               
        this.observer.observe(...);
        ...       
    }
    onIntersection(entries, observer) {
        ...
        var test = this.a.b;
        ...
    }
}

而当运行它时，我在执行 onIntersection() 时出现错误。错误是：Uncaught TypeError: Cannot read 属性 'b' of undefined。我如何将 ObjectOne 的 'this' 实例传递给 onIntersection() 函数？

Answer 1

感谢Heretic Monkey for useful link How to access the correct this inside a callback? - it was helpful and give me a direction for search. And more helpful information was at Use of the JavaScript 'bind' method。添加bind()函数解决问题：

var ObjectOne = {
    a : {
        b : 4,
        ...
    }        
    observer : 0,
    ...

    init() { 
        this.a.b = 5;           
        ...
        this.observer = new IntersectionObserver(this.onIntersection.bind(this), ...);               
        this.observer.observe(...);
        ...       
    }
    onIntersection(entries, observer) {
        ...
        var test = this.a.b;
        ...
    }
}

IntersectionObserver: "Uncaught TypeError: Cannot read property of undefined" when called onIntersection()

IntersectionObserver: "Uncaught TypeError: Cannot read property of undefined" when called onIntersection()

javascript

properties

object

undefined