数组、字符串、日期常用操作

1. 字符串

    var a = 'string'
    console.log(a.slice(2, 4)) //截取下标 2,3
    console.log(a.substring(2, 4)) //截取下标 2, 3
    console.log(a.substr(2, 4)) //2开始，取4位
        // a.lastIndexOf()返回字符串中指定字符最后一次出现的位置
    console.log(a.split('')) //转数组
      // toUpperCase()把字母转换为大写
      // toLowerCase()把字母转换为小写

2. 数组

    var b = ['a', 'b', 'c', 'd', 'f', 'g'];
    console.log(b.slice(2, 4)) //截取 下标 2,3 新数组 [c,d]
    console.log(b) //不改变原数组

    console.log(b.splice(3, 1, 'adf')) //可3个参数 开始，数量，替换元素 把d换为adf
    console.log(b) //改变原数组

    console.log(b.join(',')) //转字符串
    console.log(b) //不变原数组

3. 日期

var d= new Date(year, month, 0).getDate()   //某月天数

/**
 * @description: 格式化日期
 * @param {*} formatStr 日期格式
 */
Date.prototype.Format = function (formatStr) {
    var str = formatStr;
    var Week = ['日', '一', '二', '三', '四', '五', '六'];
    str = str.replace(/yyyy|YYYY/, this.getFullYear());
    str = str.replace(/yy|YY/, (this.getYear() % 100) > 9 ? (this.getYear() % 100).toString() : '0' + (this.getYear() % 100));
    var month = this.getMonth() + 1;
    str = str.replace(/MM/, month > 9 ? month.toString() : '0' + month);
    str = str.replace(/M/g, month);

    str = str.replace(/w|W/g, Week[this.getDay()]);

    str = str.replace(/dd|DD/, this.getDate() > 9 ? this.getDate().toString() : '0' + this.getDate());
    str = str.replace(/d|D/g, this.getDate());

    str = str.replace(/hh|HH/, this.getHours() > 9 ? this.getHours().toString() : '0' + this.getHours());
    str = str.replace(/h|H/g, this.getHours());
    str = str.replace(/mm/, this.getMinutes() > 9 ? this.getMinutes().toString() : '0' + this.getMinutes());
    str = str.replace(/m/g, this.getMinutes());

    str = str.replace(/ss|SS/, this.getSeconds() > 9 ? this.getSeconds().toString() : '0' + this.getSeconds());
    str = str.replace(/s|S/g, this.getSeconds());
    return str;
}
console.log(new Date().Format("yyyy/MM/dd/星期w hh:mm:ss"));