for-in.js // for in hasOwnProperty prototypefunction P(){ this.name = 'sigma';}P.prototype.age = 18;var a = new P();// code 1for( let key in a){ console.log( key );}// code 2for (let key in a) { a.hasOwnProperty( key ) console.log(key);}` 伪
// for in & hasOwnProperty & prototype
function P(){
this.name = 'sigma';
}
P.prototype.age = 18;
var a = new P();
// code 1
for( let key in a){
console.log( key );
}
// code 2
for (let key in a) {
a.hasOwnProperty( key ) && console.log(key);
}`
伪造hasOwnProperty
function P(){
this.name = 'sigma';
}
P.prototype.age = 18;
P.prototype.hasOwnProperty = function( ){ // 伪造
return false;
}
var a = new P();
for( let key in a){
a.hasOwnProperty( key ) && console.log(key);
}