mst

var i = 0
Object.defineProperty(window,‘x‘,{
    get(){
        return ++i
    }
})
function Fn(){
    if(this.constructor == Fn){
        this.id =i
    }else{
        let obj = {}
        obj.__proto__ = Fn.prototype
        obj.id = i
        return obj
    }
}

function changeStr(str = ‘hello-world-aaaa‘){
    let s = ‘‘
    let arr = str.split(‘-‘)
    for(let i = 0;i < arr.length;i++){
        let item = arr[i]
        item = item.replace(item[0],item[0].toUpperCase())
        s += item
    }
    return s
}

function flat(arr = [1,2,3,[4,5,[6,7]]],deep = 0){
    if(deep <= 0){
        return arr
    }
    if(deep == Number.Infinity){
        while(arr.some(Array.isArray)){
            arr = [].concat(...arr)
        }
        return arr
    }
    while(arr.some(Array.isArray) && deep > 0){
        arr = [].concat(...arr)
        deep--
    }
    return arr
}