Js代码片段

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获取日期字符串

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// [javascript Date format(js日期格式化)(转) - 先锋之客 - 博客园](https://www.cnblogs.com/xianfengzhike/p/9656382.html)
function format(date, format) {
  let o = {
    "M+": date.getMonth() + 1, // month
    "d+": date.getDate(), // day
    "h+": date.getHours(), // hour
    "m+": date.getMinutes(), // minute
    "s+": date.getSeconds(), // second
    "q+": Math.floor((date.getMonth() + 3) / 3), // quarter
    S: date.getMilliseconds() // millisecond
  };
  if (/(y+)/.test(format)) {
    format = format.replace(
      RegExp.$1,
      (date.getFullYear() + "").substr(4 - RegExp.$1.length)
    );
  }
  for (var k in o) {
    if (new RegExp("(" + k + ")").test(format)) {
      format = format.replace(
        RegExp.$1,
        RegExp.$1.length == 1 ? o[k] : ("00" + o[k]).substr(("" + o[k]).length)
      );
    }
  }
  return format;
}

function getYearMonthDay(date) {
  return format(date || new Date(), "yyyyMMdd");
}

function getYearMonth(date) {
  return format(date || new Date(), "yyyyMM");
}

console.log(getYearMonthDay());
console.log(getYearMonth());
console.log(getYearMonthDay(new Date(1999, 1, 3)));
console.log(getYearMonth(new Date(1999, 1, 3)));

身份证验证

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const isIDCard = function(str) {
  // 验证是否身份证号
  var city = {
    11: "北京",
    12: "天津",
    13: "河北",
    14: "山西",
    15: "内蒙古",
    21: "辽宁",
    22: "吉林",
    23: "黑龙江 ",
    31: "上海",
    32: "江苏",
    33: "浙江",
    34: "安徽",
    35: "福建",
    36: "江西",
    37: "山东",
    41: "河南",
    42: "湖北 ",
    43: "湖南",
    44: "广东",
    45: "广西",
    46: "海南",
    50: "重庆",
    51: "四川",
    52: "贵州",
    53: "云南",
    54: "西藏 ",
    61: "陕西",
    62: "甘肃",
    63: "青海",
    64: "宁夏",
    65: "新疆",
    71: "台湾",
    81: "香港",
    82: "澳门",
    91: "国外"
  };

  // 基础验证，长度验证
  if (!str || !/^\d{17}(\d|x)$/i.test(str)) {
    return false;
  }

  // 验证地址编码
  if (!city[parseInt(str.substr(0, 2))]) {
    return false;
  }

  // 验证出生日期
  var birthdayStr =
    str.substr(6, 4) + "/" + str.substr(10, 2) + "/" + str.substr(12, 2);
  var birthday = new Date(birthdayStr);
  if (!birthday) return false;
  var transBirthdayStr =
    birthday.getFullYear() +
    "/" +
    (birthday.getMonth() >= 9
      ? birthday.getMonth() + 1
      : "0" + (birthday.getMonth() + 1)) +
    "/" +
    (birthday.getDate() >= 10 ? birthday.getDate() : "0" + birthday.getDate());
  if (birthdayStr != transBirthdayStr) {
    // 日期有误
    return false;
  }

  // 验证长度和校验位
  if (str.length == 18) {
    str = str.split("");
    //∑(ai×Wi)(mod 11)
    //加权因子
    var factor = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
    //校验位
    var parity = [1, 0, "X", 9, 8, 7, 6, 5, 4, 3, 2];
    var sum = 0;
    var ai = 0;
    var wi = 0;
    for (var i = 0; i < 17; i++) {
      ai = str[i];
      wi = factor[i];
      sum += ai * wi;
    }
    var last = parity[sum % 11];
    if (parity[sum % 11] != str[17].toUpperCase()) {
      return false;
    }
  }

  return true;
};

设定参数必须传递

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function throwIfMissing() {
  throw new Error("Missing parameter");
}

function foo(mustBeProvided = throwIfMissing()) {
  return mustBeProvided;
}

foo();
// Error: Missing parameter

为浮点数运算部署一个误差检查函数

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function withinErrorMargin(left, right) {
  return Math.abs(left - right) < Number.EPSILON * Math.pow(2, 2);
}

0.1 + 0.2 === 0.3; // false
withinErrorMargin(0.1 + 0.2, 0.3); // true

1.1 + 1.3 === 2.4; // false
withinErrorMargin(1.1 + 1.3, 2.4); // true

正确返回字符串长度的函数（Unicode 字符）

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function codePointLength(text) {
  var result = text.match(/[\s\S]/gu);
  return result ? result.length : 0;
}

var s = "𠮷𠮷";

s.length; // 4
codePointLength(s); // 2

apply & call

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var a = { x: 1 };
var b = { x: 2 };
function f() {
  console.log(this.x);
}
a.f = f;
b.f = f;
f.apply(a); //1
f.apply(b); //2

返回对象的类

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// p214
function classof(o) {
  return Object.prototype.toString.call(o).slice(8, -1);
}

输出对象的类：Object.prototype.toString.call

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Object.prototype.toString.call(1);
("[object Number]");

Object.prototype.toString.call(function() {});
("[object Function]");

typeof 得到的是类型；

How to pass url query params

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function getUrl(url, options) {
  if (!isEmptyObject(options)) {
    url += (url.indexOf("?") === -1 ? "?" : "&") + queryParams(options);
  }
  return url;
}

function queryParams(params) {
  return Object.keys(params)
    .map(k => encodeURIComponent(k) + "=" + encodeURIComponent(params[k]))
    .join("&");
}

// 判断对象是否为空 https://stackoverflow.com/questions/4994201/is-object-empty
function isEmptyObject(obj) {
  if (obj == null) return true;
  if (obj.length > 0) return false;
  if (obj.length === 0) return true;
  if (typeof obj != "object") return true;

  for (var name in obj) {
    if (obj.hasOwnProperty(name)) {
      return false;
    }
  }
  return true;
}

var url = getUrl("http://lyloou.com", {});
console.log(url);

对象转数组

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json2array = function(json) {
  let result = [];
  let keys = Object.keys(json);
  keys.forEach(function(key) {
    result.push(json[key]);
  });
  return result;
};

arr2Obj = function(array) {
  var obj = new Object();
  if (typeof array == "object") {
    for (var i in array) {
      var thisEle = convArrToObj(array[i]);
      obj[i] = thisEle;
    }
  } else {
    obj = array;
  }
  return obj;
};

输入银行卡号，4 位自动加上空格分隔

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
  <head>
    <title>test</title>
    <script type="text/javascript">
      window.onload = function() {
        document.getElementById("test").onkeyup = function() {
          this.value = this.value
            .replace(/\s/g, "")
            .replace(/\D/g, "")
            .replace(/(\d{4})(?=\d)/g, "$1 ");
        };
      };
    </script>
  </head>
  <body>
    <input type="text" id="test" />
  </body>
</html>

在前台读取数字时自动忽略空格

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// 这样的话会把a b c d读取为abc
String newStr = "a b c".replaceAll(" ","");

正则摘取文字

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// var input = "'Warehouse','Local Release','Local Release DA'";
var input =
  '【丝路亚心】250gX4<font color="red">核桃仁</font> 原味生<font color="red">核桃核桃仁</font> 新疆特产, <font color="red">123445</font>bcdef';
var regex = /<font[^>]+?>(.*?)<\/font>/g;

var matches,
  output = [];
while ((matches = regex.exec(input))) {
  output.push(matches[1]);
}
console.log(matches);
console.log(output);

function replaceText(text) {
  return text.replace(/<font[^>]*>/g, "").replace(/<\/font>/g, "");
}

var newStr = replaceText(input);
console.log(newStr);

var arr = [];
for (let i in output) {
  let val = output[i];
  console.log(val);
  let index = newStr.indexOf(val);
  arr.push({ type: "normal", value: newStr.substring(0, index) });
  arr.push({ type: "highlight", value: val });
  newStr = newStr.substring(index + val.length);
}

if (newStr) {
  arr.push({ type: "normal", value: newStr });
}

console.log(arr);
// [{"type":"normal","value":"【丝路亚心】250gX4"},{"type":"highlight","value":"核桃仁"},{"type":"normal","value":" 原味生"},{"type":"highlight","value":"核桃核桃仁"},{"type":"normal","value":" 新疆特产, "},{"type":"highlight","value":"123445"},{"type":"normal","value":"bcdef"}]