es6数组去重、数组中的对象去重 && 删除数组(按条件或指定具体元素 如:id)&& 筛选去掉没有子组件的父组件 && 获取数组对象中重复的数据
// 数组去重 { const arr = [1,2,3,4,1,23,5,2,3,5,6,7,8,undefined,null,null,undefined,true,false,true,‘中文‘,‘‘,‘‘,‘hello‘,‘中文‘]; // 第一种 const r = [...new Set(arr)]; console.log(r); // [1, 2, 3, 4, 23, 5, 6, 7, 8, undefined, null, true, false, "中文", "", "hello"] // 第二种 const R = arr.reduce((all,name) => all.includes(name) ? all :[...all,name],[]); console.log(R); // [1, 2, 3, 4, 23, 5, 6, 7, 8, undefined, null, true, false, "中文", "", "hello"] // 第三种 const k = arr.filter((item, i) => i === arr.indexOf(item)); console.log(k); // [1, 2, 3, 4, 23, 5, 6, 7, 8, undefined, null, true, false, "中文", "", "hello"] } // 统计每个元素在数组中出现的次数 { const arr = [‘zhangsan‘, ‘lisi‘, ‘wangwu‘, ‘zhangsan‘, ‘lisi‘, ‘wangwu‘,‘zhaosi‘,‘liuneng‘]; const r = arr.reduce((all, name) =>{ if(name in all){ all[name]++ }else{ all[name] = 1; } return all; },{}); console.log(r); // {zhangsan: 2, lisi: 2, wangwu: 2, zhaosi: 1, liuneng: 1} } // 数组对象去重 { const arr = [ { name:‘zhangsan‘, age:12 }, { name:‘lisi‘, age:14 }, { name:‘zhangsan‘, age:12 }, { name:‘lisi‘, age:14 }, { name:‘zhangsan‘, age:12 }, { name:‘lisi‘, age:14 }, { name:‘zhangsan‘, age:12 }, { name:‘wangwu‘, age:16 }, { name:‘wagnwu‘, age:16 }, { name:‘lisi‘, age:14 }, ] // 根据 age 去重 // 方法一 const age = ‘age‘; const r = arr.reduce((all, next) => all.some((atom) => atom[age] == next[age]) ? all : [...all, next],[]); console.log(r); }
//指定具体元素//删除id=5的 let arr = [ { id: 1, name: '北京' }, { id: 2, name: '上海' }, { id: 3, name: '深圳' }, { id: 4, name: '广州' }, { id: 5, name: '青岛' } ] arr.splice(arr.findIndex(item=>item.id==5),1)
//find方法用于查找第一个符合条件的数组成员,如果没有找到返回undefind
let target = arr.find((item,index) => { return item.id ==1 }) console.log(target)
//删除id大于3的(只保留小于等于3) let arr2 = arr.reduce((total, current) => { current.id<= 3 && total.push(current); return total; }, []);
//筛选去掉没有子组件的父组件 (parentId为0代表是父组件) let arr = [ { name:'1', id:1, parentId:0 },{ name:'3', id:3, parentId:0 },{ name:'2', id:2, parentId:0 },{ name:'1333', id:13, parentId:1 },{ name:'2444', id:24, parentId:2 }] arr = arr.filter((x, index, self)=>{ // x : 数组每一项的值 // index: 每一项的下标 // self: 当前数组 return x.parentId!=0 || self.some((atom) => atom['parentId'] == x['id'] ) })
//使用filter与findIndex数组对象去重 let arr = [ {id: 1,name: '张三'}, {id: 2,name: '李四'}, {id: 1,name: '张三'}, {id: 2,name: '李四'} ]; let nArr = arr.filter((currentValue, currentIndex, selfArr) = >{ return selfArr.findIndex(x = >x.name === currentValue.name) === currentIndex }); console.log(nArr);
//获取重复数据用!== 筛掉重复数据用=== arr是一个数组对象 const repeatArr = arr.filter((item,index,data)=>{ return arr.findIndex(t=>t.id===item.id) !== index; })