Comments (2)
这里确实有问题,函数不是构造函数,没有 new,调用时 this 都是指向 window。不会打印函数内对应的变量 a
应该改为
var a = 5
function callback() {
console.log('-- callback this', this, this.a, '--')
}
function validate() {
console.log('-- validate this', this, this.a, '--')
}
function showPrompt(title, validate, callback) {
validate()
callback()
}
showPrompt('1', validate, callback) // 5 5
showPrompt('1', validate.bind({a: 2}), callback.bind({a: 1})) // 2 1
或者
var a = 5
var callback = {
a: 1,
handler() {
console.log(this, this.a)
}
}
var validate = {
a: 2,
handler() {
console.log(this, this.a)
}
}
function showPrompt(title, validate, callback) {
validate()
callback()
}
showPrompt('1', validate.handler, callback.handler) // 5 5
showPrompt('1', validate.handler.bind(validate), callback.handler.bind(callback)) // 2 1
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谢谢,看了您的学习笔记,对我扩展知识广度帮助很大,感谢!
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