JS-数据处理

const arr = [ {id: 1, score: 1}, {id: 2, score: 2}, {id: 3, score: 4}];
const newValue = {id: 3, score: 3}
const result = arr.map(x => x.id === newValue.id ? newValue : x); 
document.write(JSON.stringify(result)  + "<br />")
//或者
const updated = arr.map(function(item){
    return item.id == newValue.id ? newValue : item ;
});
document.write(JSON.stringify(updated)  + "<br />")

const numbers = [1, 2, 1, 1, 2, 1, 3, 4, 1 ];
const uniq = [...new Set(numbers)] // => [ 1, 2, 3, 4 ];
const uniq2 = Array.from(new Set(numbers)) // => [ 1, 2, 3, 4 ];
document.write(JSON.stringify(uniq)  + "<br />")
document.write(JSON.stringify(uniq2)  + "<br />")

 // 根据属性删除数组中的对象,利用filter进行过滤数组中id相同的项
 const initial = [ {id: 1, score: 1}, {id: 2, score: 2}, {id: 3, score: 4}];
 const removeId = 3;
 const without3 = initial.filter(x => x.id !== removeId);
document.write(JSON.stringify(without3)  + "<br />")

//利用es6的 ...运算符将其他属性和ａ属性分开来
const obj = {a: 1, b: 2, c: 3};
const {a, ...newObj} = obj;
document.write(JSON.stringify(newObj)  + "<br />")

//去掉s3中的2和4
 const s3 = [ 1, 2, 3, 4, 5, 4, 5, 6, 2, 2, 4 ];
 const s2 = [ 2, 4 ];
 const subtracted1 = s3.filter(x => s2.indexOf(x) < 0);
 document.write(JSON.stringify(subtracted1)  + "<br />")

let person = [
     {id: 0, name: "小明"},
     {id: 1, name: "小张"},
     {id: 2, name: "小李"},
     {id: 3, name: "小孙"},
     {id: 1, name: "小周"},
     {id: 2, name: "小陈"},   
];

let obj = {};

let peon = person.reduce((cur,next) => {
    obj[next.id] ? "" : obj[next.id] = true && cur.push(next);
    return cur;
},[]) //设置cur默认类型为数组，并且初始值为空的数组
document.write(JSON.stringify(peon)  + "<br />")

let flag = 'true';//支持大小写
eval(flag.toLowerCase())

 /**
  * 根据传入name获取url后缀中数据
  * @param {参数名} name 
  */
 export const GetQueryString = (name) => {
    var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)");
    var r = decodeURI(window.location.search.substr(1)).match(reg);
    if (r != null)return unescape(r[2]);
    return null;
}