采用多种获取原型的方式，多种使用Symbol的方式让你了解他们的使用
手写bind
Function.prototype._bind = function(instance = window) {
if( instance === null || instance === undefined ) return undefined
if( typeof instance !== 'object' ) instance = Object.create(Object.getPrototypeOf(instance))
const fn = Symbol()
instance[fn] = this
return (...args) => {
const res = instance[fn](...args)
delete instance[fn]
return res
}
}
2. 手写一个call
Function.prototype._call = function(instance = window, ...args){
if( instance === null || instance === undefined ) return undefined
if( typeof instance !== 'object' ) instance = Object.getPrototypeOf(instance)
const fn = Symbol('fn')
instance[fn] = this
const res = instance[fn](...args)
delete instance[fn]
return res
}
3. 手写一个apply
Function.prototype._apply = function(instance = window, args = [] ) {
if( instance === null || instance === undefined ) return undefined
if( typeof instance !== 'object' ) instance = instance.__proto__
instance[Symbol.for('fn')] = this
const res = instance[Symbol.for('fn')](...args)
delete instance[Symbol.for('fn')]
return res
}
