SOURCE

let resource = {
    a: 'a',
    address: {
        city: 'beijing'
    },
    arr: [1, 3 , 5]
}
console.log(resource.address.city)
let tmp  = deepCopy(resource)
tmp.address.city = 'shanghai'
console.log(resource.address.city)


function deepCopy(obj={}) {
    if (typeof obj !== 'object' || obj == null){
        return obj
    }
    // 初始化
    let result
    if (obj instanceof Array) {
        result = []
    } else{
        result = {}

    }

    for(let key in obj){
        // 保证key 不是原型属性
        if (obj.hasOwnProperty(key)){
            // !important 递归调用
            result[key] = deepCopy(result[key])

        }
    }
    return result

}