JS的某些常用方法合集

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数组对象去重

1. 方法一

   let arr = [{ id: 1, test: '哈哈' }, { id: 2, test: '呵呵' }, { id: 1, test: '哈哈' }, { id: 3, test: '哈哈' }]
           var obj = {};
           arr = arr.reduce((item, next) => {
               obj[next.id] ? '' : obj[next.id] = true && item.push(next);
               return item;
   
           }, []);
           console.log(arr);​

2. 方法二

   function unique(arr, key) {
       return arr.filter((item, index, arr) => {
           return arr.findIndex(row => {
               return row[key] == item[key]
           }) == index
       })
   }​

日期分割

1. 方法一

       function insertStr(soure, firstPosition, firstStr, secondPosition, secondStr) {
                   soure = soure.slice(0, firstPosition) + firstStr + soure.slice(firstPosition)
                   return soure.slice(0, secondPosition) + secondStr + soure.slice(secondPosition)
               }
   
               let currentTime = "20210323"
   
               console.log(insertStr(currentTime, 4, '-', 7, '-'))//2021-03-23​