日期，字符串和对象

获取2017-06-10格式的日期

function formateDate(dt){
    if(!dt){
        dt = new date();
    }
    var year = dt.getFullYear();
    var month = dt.getMonth() + 1;
    var date = dt.getDate();

    if(month<10){
        month = "0" + month;
    }
    if(date<10){
        date = "0" + date;
    }
    return year + "-" + month + "-" + date;
}
var dt = new Date();
var formateDate = formateDate(dt);
console.log(formateDate);  // 2017-12-08

获取随机数，要求是长度一致的字符串格式

var random = Math.random();
random = random + '0000000000'; // 后面加上10个0
random = random.slice(0,10);
console.log(random);  // 0.95975987

写一个能遍历对象和数组的forEach函数

function forEach(obj,fn){
    if(obj instanceof Array){
        obj.forEach((item,index) => {
            fn(index,item);
        });
    }else{
        for(key in obj){
            if(obj.hasOwnProperty(key)){
                fn(key,obj[key]);
            }
        }
    }
}
var arr = ['a','b','c'];
forEach(arr,(index,item)=>{
    console.log(index,item);
});
// 0 'a'
// 1 'b'
// 2 'c'

var obj = {x:100,y:200};
forEach(obj,(index,item)=>{
    console.log(index,item);
});
// x 100
// y 200