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JS implementation of new

2022-04-23 03:15:00 【GeXueliu】

Realization new The operator

  1. Create a blank object
  2. Modify the prototype of the blank object to the prototype of the constructor
  3. this Point to a blank object , And execute the constructor
  4. Returns the object 
   function Animal(name,age) {
    
        this.name = name;
        this.age = age;
    }
    function _new(constructor,...args) {
    
        let instance = {
    };
        // instance._proto_ = constructor.prototype;  Are four underscores 
        instance.__proto__ = constructor.prototype; 
        let result = constructor.call(instance,...args); 
        return  typeof result === 'object'? result:instance; //  Returns the non empty object returned by the constructor , Otherwise return the created object 
    }
 let a = _new(Animal,'lli','2');
 console.log('a',a)
 console.log(a instanceof Animal); 
 // expected output: true

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本文为[GeXueliu]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/04/202204220627323115.html

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