some demos

摘要：数组中连续的一个或多个整数组成一个子数组，每个子数组都有一个和。求所有子数组的和的最大值，要求时间复杂度为。输出结果类数组转成数组直接遍历这种方法是借用了数组原型中的方法，返回一个数组方法从一个类似数组或可迭代对象中创建一个新的数组实例。

</>复制代码 
import "../css/detail.css";
// 找到字符串中重复次数最多的字符
function findMax(str) {
  let maxChar = "";
  let maxValue = 1;
  if (!str.length) return;
  let arr = str.replace(/s/g, "").split("");
  let obj = {};
  for (let i = 0; i < arr.length; i++) {
    if (!obj[arr[i]]) {
      obj[arr[i]] = 1;
    } else {
      obj[arr[i]]++;
    }
  }
  let keys = Object.keys(obj);
  for (let j = 0; j < keys.length; j++) {
    if (obj[keys[j]] > maxValue) {
      maxValue = obj[keys[j]];
      maxChar = keys[j];
    }
  }
  return {
    maxChar, maxValue
  }
}
function findMax1() {
  let maxChar = "";
  let maxValue = 1;
  let h = {};
  if (!str.length) return;
  let arr = str.replace(/s/g, "").split("");
  for (let i = 0; i < arr.length; i++) {
    let a = arr[i];
    h[a] === undefined ? h[a] = 1 : h[a]++;
    if (h[a] > maxValue) {
      maxChar = a;
      maxValue = h[a];
    }
  }
  return {
    maxChar, maxValue
  }
}
function findMax2() {
  let maxChar = "";
  let maxValue = 1;
  if (!str.length) return;
  let arr = str.replace(/s/g, "").split("");
  let obj = arr.reduce((acc, curVal) => {
    acc[curVal] ? acc[curVal]++ : acc[curVal] = 1;
    if (acc[curVal] > maxValue) {
      maxChar = curVal;
      maxValue = acc[curVal];
    }
    return acc;
  }, {}) 
  return {
    maxChar, maxValue
  }
}

</>复制代码 
/* 
  d 任意一个数字，0~9 中的任意一个
  w 任意一个字母或数字或下划线，也就是 A~Z,a~z,0~9,_ 中任意一个
  s 包括空格、制表符、换页符等空白字符的其中任意一个
. 小数点可以匹配除了换行符（
）以外的任意一个字符 
*/
function findMax3(str) {
  let maxChar = "";
  let maxValue = 1;
  if (!str.length) return;
  let arr = str.replace(/s/g, "").split("");
  let obj = {};
  str.replace(/s/g, "").replace(/(w)/g, (word, p) => {
    obj[p] ? obj[p]++ : obj[p] = 1;
    if (obj[p] > maxValue) {
      maxValue = obj[p];
      maxChar = p;
    }
  });
  return {
    maxChar, maxValue
  }
}
function findMax4(str) {
  let maxChar = "";
  let maxValue = 1;
  if (!str.length) return;
  let arr = str.replace(/s/g, "").split("");
  Array.prototype.getMost = function() {
    let obj = this.reduce((acc, cur) => {
      acc[cur] ? acc[cur]++ : acc[cur] = 1;
      acc.max = acc[cur] > acc.max ? acc[cur] : acc.max;
      acc.key = acc[cur] > acc.max ? cur : acc.key;
      return acc;
    }, {});
    return obj;
  }
  // return arr.getMost();
}
const str = "this is a test 222222 ts project. skajdf; 222sldjfwel p"

</>复制代码 
const reducer = (accumulator, currentValue, b, c) => {
  let obj = {};
  obj[b] = currentValue;
  return obj;
}
const array1 = [1, 2, 3, 4];
// console.log(array1.reduce(reducer));
console.log(findMax(str));
console.log("findMax1", findMax4(str));

</>复制代码 
/**
 * 输入一个整形数组，数组里有正数也有负数。数组中连续的一个或多个整数组成一个子数组，每个子数组都有一个和。 求所有子数组的和的最大值，要求时间复杂度为O(n)。
 */
function findMaxSubArr(arr) {
  console.log(arr)
  let max = arr[0];
  let currSum = 0;
  for (let i = 0; i < arr.length; i++) {
    if (currSum < 0) {
      currSum = arr[i];
    } else {
      currSum += arr[i]; 
    }
    if (currSum > max) {
      max = currSum;
    }
  }
  return max;
}
// console.log("maxsubarr", findMaxSubArr([1, -2, 3, 10, -4, 7, 2, -5]));

</>复制代码 
// 输出结果
console.log("begin");
setTimeout(() => {
  console.log("settimeout 1")
  Promise.resolve().then( () => {
    console.log("promise 1")
    setTimeout(() => {
      console.log("settimeout 2");
    });
  }).then(() => {
    console.log("promise 2");
  })
}, 0);
console.log("end");

</>复制代码 
/**
 * 类数组转成数组
 */
const nodes = document.querySelectorAll("div");
// nodes.map(item => {});
// 1.for直接遍历
// 2.这种方法是借用了数组原型中的slice方法，返回一个数组
Array.prototype.slice.call(nodes).map(item => {});
[].slice.call(nodes).map(item => {console.log()});
// 3.Array.from() 方法从一个类似数组或可迭代对象中创建一个新的数组实例。
Array.from(nodes).map(item => {})
// 4.同样是ES6中新增的内容，扩展运算符（…）也可以将某些数据结构转为数组
const nodeList = [...nodes];
function getlist(a,b,c,d) {
  // console.log(arguments);
  // console.log([...arguments][0])
}
getlist(11, 2, 3, 4);

</>复制代码 
// 使用reduce方法实现forEach、map、filter
const arr1 = [12, 21, 3];
const arr2 = arr1.map(function(item) {
  // console.log(this, item)
  return item*2
}, { msg: "mapping" })
// console.log(arr1, arr2)

</>复制代码 
// github上的
Array.prototype.selfMap = function () {
  const ary = this
  const result = []
  const [ fn, thisArg ] = [].slice.call(arguments)
  if (typeof fn !== "function") {
    throw new TypeError(fn + "is not a function")  
  }
  for (let i = 0; i < ary.length; i++) {
    result.push(fn.call(thisArg, ary[i], i, ary))
  }
  return result
}
Array.prototype.reduceMap = function (fn, thisArg) {
  // return (list) => {
      // 不怎么愿意写下面这两个判断条件
      const list = this
      if (typeof fn !== "function") {
          throw new TypeError(fn + "is not a function")  
      }
      if (!Array.isArray(list)) {
          throw new TypeError("list must be a Array")
      }
      if (list.length === 0) return []
      return list.reduce((acc, value, index) => {
          return acc.concat([ fn.call(thisArg, value, index, list) ])
      }, [])
  // }
}

</>复制代码 
// mine
Array.prototype.imitateMap = function () {
  const list = this;
  const result = []
  const [fn, thisArg] = [].slice.call(arguments)
  if (typeof fn !== "function") {
    throw new TypeError(fn + "is not a function");
  }
  for (let i = 0; i < list.length; i++) {
    result.push(fn.call(thisArg, list[i], i, list));
  }
  return result;
}
Array.prototype.imitateReduceMap = function () {
  const list = this;
  const result = []
  const [fn, thisArg] = [].slice.call(arguments)
  if (typeof fn !== "function") {
    throw new TypeError(fn + "is not a function");
  }
  if (!Array.isArray(list)) {
    throw new TypeError(list + "is not a Array");
  }
  return list.reduce((acc, curValue, index) => {
    return acc.concat([fn.call(thisArg, curValue, index, list)]);
  }, [])
}

</>复制代码 
const imitateReduceMap1 = function (fn, thisArg) {
  return (list) => {
    const result = []
    if (typeof fn !== "function") {
      throw new TypeError(fn + "is not a function");
    }
    if (!Array.isArray(list)) {
      throw new TypeError(list + "is not a Array");
    }
    return list.reduce((acc, curValue, index) => {
      return acc.concat([fn.call(thisArg, curValue, index, list)]);
    }, [])
  }
}
console.log("imitateMap", arr1, arr1.imitateMap(function(item) {
  console.log("imitateMap this", this)
  return item + 1
}, { msg: "mapping" }) )
console.log("imitateReduceMap", [ 1, 2, 3 ].imitateReduceMap(x => x + 1));
console.log("imitateReduceMap1", imitateReduceMap1(x => x + 1)([ 1, 2, 3 ]));

</>复制代码 
/**
 * 实现repeat方法
 */
function repeat(func, times, wait) {
  return (str) => {
    let count = 0;
    const timer = setInterval(() => {
      if (count < times) {
        // func.call(this, str);
        count++;
      } else {
        clearInterval(timer);
      }
      
    }, wait);
  }
}
const repeatFunc = repeat(alert, 3, 2000)
repeatFunc("helloworld");

</>复制代码 
/**
 * 实现一个简单的双向绑定
 * 1.发布-订阅模式
 * 2.脏值检测
 * 3.数据劫持
 * Vue.js 采用的是 数据劫持+发布/订阅模式 的方式，通过 Object.defineProperty() 来劫持各个属性的 setter/getter， 在数据变动时发布消息给订阅者（Wacther）, 触发相应的监听回调
 */
// 基于Object.defineProperty 实现数据劫持，利用了对Vue.js实现双向绑定的思想
const obj = {}
Object.defineProperty(obj, "txt",{
  get:function(){
    return obj
  },
  set:function(newValue){
    document.getElementById("txt").value = newValue
    document.getElementById("show-txt").innerHTML = newValue
  }
})
document.addEventListener("keyup", function(e){
  obj.txt = e.target.value
})