JS判断对象中是否拥有某属性
obj[item]
const obj = { a: 1, b: 2 } console.log(obj['c']) //undefined
in运算符
const obj = { a: 1, b: 2 } console.log('c' in obj) // false
hasOwnProperty
const obj = { a: 1, b: 2 } console.log(obj.hasOwnProperty('c')) //false
obj[item]
const obj = { a: 1, b: 2 } console.log(obj['c']) //undefined
in运算符
const obj = { a: 1, b: 2 } console.log('c' in obj) // false
hasOwnProperty
const obj = { a: 1, b: 2 } console.log(obj.hasOwnProperty('c')) //false
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