In a function, in strict mode,thisisundefined. In an event,thisrefers to theelementthat received the event. Methods likecall(),apply(), andbind()can referthistoany object. Note thisis not a variable. It is a keyword. You cannot change the value ofthis. ...
In most cases, the value of this is determined by how a function is called (runtime binding). ES5 introduced the bind() method to set the value of a function's this regardless of how it's called, and ES2015 introduced arrow functions which don't provide their own this binding (it re...
In most cases, the value of a function'sthisargument is determined by how the function is called. This lesson explains whatthisrefers to when we call plain function. Marius points out how functions behave differently in strict and non-strict mode."use strict"mode defaultsthisto undefined and ...
In most cases, the value of a function'sthisargument is determined by how the function is called. This lesson explains whatthisrefers to when we call plain function. Marius points out how functions behave differently in strict and non-strict mode."use strict"mode defaultsthisto undefined and ...
log(this === undefined); // => true return a * b; } // multiply() function invocation with strict mode enabled // this in multiply() is undefined multiply(2, 5); // => 10 当使用严格模式调用 multiply(2, 5) 的时候,this 就是undefined。 严格模式不仅对当前作用域有效,它内部的作用...
当在JavaScript中遇到TypeError: undefined is not a function的错误时，主要原因是尝试调用了一个尚未定义或者还未初始化的函数。这种情况可能出现在以下两种情景中：1、你可能忘记定义了你试图调用的函数。例如，原本应该这样写： 如果没有定义gameDraw函数，那么在后续代码中调用gameDraw.drawBall()就会...
function hello(thing) { console.log(this + " says hello " + thing); } hello.call("Yehuda", "world") //=> Yehuda says hello world 如你所见,hello方法的调用过程中,this被绑定到"Yehuda"上,而参数是"world"。这就是JavaScript最核心、基础的函数调用方式,核心原始方法。你可以认为其他所有的函数...
javascript之function的this 一、this 的定义 与 函数的调用 在 javascript 中, function 中的 this 指代的是: 调用 function 执行时的上下文。 也就是说,调用哪个 ...
This behavior has changed in ECMAScript 5 only when using strict mode[2]: // this: hello("world") // desugars to: hello.call(undefined,"world"); 1. 2. 3. 4. 5. The short version is: a function invocation like fn(...args) is the same as fn.call(...
「The this keyword evaluates to the value of the ThisBinding of the current execution context.」「this 这个关键字代表的值为当前执行上下文的ThisBinding。」然后再来看看MDN 对this 的定义：「In most cases, the value of this is determined by how a function is called.」「在大多数的情况下，this ...