正如MDN文档所说: Until arrow functions, every new function defined its own this value based on how the function was called。This proved to be less than ideal with an object-oriented style of programming. 箭头函数 箭头函数的this取值,规则非常简单,因为this在箭头函数中,可以看做一个普通变量。 An ...
“this”是 JavaScript 的一个关键字,它具体的含义依赖于使用的环境。 至于在学习 JavaScript 的时候,”this”如此让人迷惑就是因为它的环境又基于你如何使用它。 你甚至可以把它理解成为一个动态的关键字。 我很喜欢 Ryan Morr 在Understanding Scope and Context in JavaScript中的一句话: Context is always the ...
正如MDN文档所说: Until arrow functions, every new function defined its own this value based on how the function was called。This proved to be less than ideal with an object-oriented style of programming. 箭头函数 箭头函数的this取值,规则非常简单,因为this在箭头函数中,可以看做一个普通变量。 An ...
function checkAge(age) { if (age < 18) { throw new Error("Age must be 18 or older."); } return "Access granted."; } Day 25: Modules - import and export Topics: Using import and export for Modules Description: Learn how to work with JavaScript modules. Code Example: // export.js...
关于this 的文章也够多了,有时候越描越黑,我就不再添乱了,我只负责搬运一下 MDN 文档:this,感兴趣的可以仔细阅读一下,我摘录一些最重要的话就好了。 A function’s this keyword behaves a little differently in JavaScript compared to other languages. It also has some differences between strict mode and...
[1]译者注:目前流传的译文中将 the core function invocation primitive 译为函数调用的核心原始方法 ,本文中将其作为专有名词或许更合理,不过此处为了便于初读本文的读者理解,我将其意译。事实上,Primitive是JavaScript的专有名词,MDN将其译为原始数据或者基本类型,此处应该是作者类比基本类型,给基础的函数调用方法起的...
C: Function expressions with grouping operators: var C = (function(){}); These really aren’t different from plain old function expressions and aren’t really seen in the wild (so maybe they’re just good for JavaScript quizzes?). Recently this way of declaring functions was brought up ...
Every function has the method.bind[docs], which returns a new function withthisbound to a value. The function has exactly the same behavior as the one you called.bindon, only thatthiswas set by you. No matter how or when that function is called,thiswill always refer to the passed value...
This leads to three errors in our code. // First, we’re adding properties to this in the constructor function. Again, because Arrow Functions don’t have their own this, you can’t do that. // Second, we can’t use the new keyword with an Arrow Function. This will throw a X is...
// Create obj with a method bar that returns a function that // returns its this. The returned function is created as // an arrow function, so its this is permanently bound to the // this of its enclosing function. The value of bar can be set // in the call, which in turn sets...