prototype chain

prototype_chain_examples.js

var mufasa = {
  name: "Mufasa",
  sing() {
    var inner = function() {
        console.log("inner:this", this);
    };
    var innerStrict = function() {
        'use strict';
        console.log("innerStrict:this", this);
    };
    var innerArrow = ()=>console.log("innerArrow:this", this)
    var innerArrowStrict = ()=>{
        'use strict'; // doesn't matter in an arrow function
        console.log("innerArrowStrict:this", this);
    }
    console.log("sing", this);
    inner();
    innerStrict();
    innerArrow();
    innerArrowStrict();
  }
};
var simba = {name:'Simba'};
console.log('\nmufasa.sing(); ... calling sing in the context of mufasa')
mufasa.sing();
console.log('\nmufasa.sing.call(simba); ... calling sing in the context of simba')
mufasa.sing.call(simba);
console.log('\nsimba.sing=mufasa.sing;simba.sing(); ... assigning sing to a different context')
simba.sing=mufasa.sing;simba.sing();

(function(){
    'use strict';
    // calling stored method defined with function syntax prototype inheritance in strict mode: error
    // calling stored method defined with class syntax prototype inheritance (always strict mode): error 
    // calling stored method defined with function syntax prototype inheritance in non-strict mode: this===window
    // ^ try commenting out 'use strict' above, then running it
    function FMammal (name){
      this.name=name;
    }
    FMammal.prototype.getProtoString = function(logLabel){ return protoString(this) }
    function FPet (name){
      FMammal.call(this,name);
    };
    FPet.prototype=Object.create(FMammal.prototype);
    FPet.prototype.constructor = FPet;
    const fpet = new FPet('Clyo');
    console.log('fpet.getProtoString()',fpet.getProtoString());
    const fgetProtoString = fpet.getProtoString;
    const bar={name:'bar',baz:function(){try{console.log('baz',fgetProtoString())}catch(e){console.log(`baz fgetProtoString() error ${e.message}`)}}};
    bar.baz();
    // ^ retains the global execution context it's assigned to even when called from within another method.
    // execution context and "this" binding are unrelated
    // calling context object and "this" binding are related
    try{console.log('fgetProtoString()',fgetProtoString())}catch(e){console.log(`fgetProtoString() error ${e.message}`);}
    class CMammal {
      constructor(name){this.name=name;}
      getProtoString(){ return protoString(this) }
    }
    class CPet extends CMammal {
      constructor(name){super(name);}
    }
    const cpet = new CPet('Clyo');
    console.log('cpet.getProtoString()',cpet.getProtoString());
    const cgetProtoString = cpet.getProtoString;
    try{console.log('cgetProtoString()',cgetProtoString())}catch(e){console.log(`cgetProtoString() error ${e.message}`);}
    function* yieldProto (o){while(o=o.__proto__) yield o.constructor.name;yield 'null';}
    function protoString(o){return [...yieldProto(o)].reverse().join(" < ")};
}());