js常规数组操作,es6 filter() 数组过滤方法总结
1 Array.every(x=>x)是每一个都要满足 2 3 Array.some(x=>x)是有一个满足。 4 5 Array.find(findIndex),返回符合条件的第一个值。 6 7 Array.filter(过滤成新的数组) 8 9 数组的方法分为两类 10 11 1)改变原数组 12 13 push,pop,shift,unshift,sort,reverse,splice 14 15 2)不改变原数组fliter,concat,join--> 16 17 split,toStringpush:从数组最后一位开始加数据 18 19 pop:把数组最后一位剪切 20 21 shift:在数组最前一位剪切 22 23 unshift:在数组最前一位加数 24 25 reverse:把原数组逆转 26 27 splice:arr.splice(从第几位开始,截取多少长度,在切口处添加新数据) 28 29 concat :连接join:返回字符串 30 31 slice:截取arr.slice(从该为开始截取,截取到该为)
示例 1.创建一个数组,判断数组中是否存在某个值 var newarr = [ { num: 1, val: 'ceshi', flag: 'aa' }, { num: 2, val: 'ceshi2', flag: 'aa2' } ] console.log(newarr.filter(item => item.num===2 )) 2.也可以通过上面方法过滤掉num为2的留下num为1的 var newarr = [ { num: 1, val: 'ceshi', flag: 'aa' }, { num: 2, val: 'ceshi2', flag: 'aa2' } ] console.log(newarr.filter(item => item.num!=2 ))
3.去掉空数组空字符串、undefined、null var arr = ['1','2',undefined, '3.jpg',undefined] var newArr = arr.filter(item => item) console.log(newArr) var arr = ['1','2',null, '3.jpg',null] var newArr = arr.filter(item => item) console.log(newArr) >//空字符串里面不能包含空格 var arr = ['1','2','', '3.jpg',''] var newArr = arr.filter(item => item) console.log(newArr) 4.去掉数组中不符合项 var arr = [20,30,50, 96,50] var newArr = arr.filter(item => item>40) console.log(newArr)
5.过滤不符合项 var arr = ['10','12','23','44','42'] var newArr = arr.filter(item => item.indexOf('2')<0) console.log(newArr)
6.数组去重 var arr = [1, 2, 2, 3, 4, 5, 5, 6, 7, 7,8,8,0,8,6,3,4,56,2]; var arr2 = arr.filter((x, index,self)=>self.indexOf(x)===index) console.log(arr2); //[1, 2, 3, 4, 5, 6, 7, 8, 0, 56] /* 7 有一个对象数组 a ,将a数中对象某个属性的值存储到B数组中 */ var porducts = [ {name:"cucumber",type:"vegetable"}, {name:"banana",type:"fruit"}, {name:"celery",type:"vegetable"}, {name:"orange",type:"fruit"}, ]; // es5 var filteredProducts = []; for(var i = 0;i < porducts.length; i ++){ if(porducts[i].type === "fruit"){ // 如果条件满足就把当前的值推入 filteredProducts.push(porducts[i]) } } // console.log(filteredProducts)//0: {name: "banana", type: "fruit"}1: {name: "orange", type: "fruit"}length: 2__proto__: Array(0) // ES6 var filter2 = porducts.filter(function(porduct){//对porducts数组对象过滤如果porduct.type === "fruit"就return出去,再用一个变量接住 return porduct.type === "fruit" }) console.log(filter2) /* 需求二 8 有一个对象数组A,过滤掉不满足以下条件对象 条件:蔬菜 数量大于0 价格小于10 */ var products = [ {name:"cucumber",type:"vegetable",quantity:0,price:1}, {name:"banana",type:"fruit",quantity:10,price:16}, {name:"celery",type:"vegetable",quantity:30,price:8}, {name:"orange",type:"fruit",quantity:3,price:6}, ]; products = products.filter(function(product){ return product.type === "vegetable" && product.quantity > 0 && product.price < 10 }) console.log(products)//0: {name: "celery", type: "vegetable", quantity: 30, price: 8}name: "celery"price: 8quantity: 30type: "vegetable"__proto__: Objectlength: 1__proto__: Array(0) /* 需求三: 9 有两个数组A,B,根据A中的ID值 ,过滤掉B数组不符合的数据 */ var post = {id:4,title:"javascript"}; var comments = [ {postId:4,content:'Angular4'}, {postId:2,content:'VUE.js'}, {postId:3,content:'Node.js'}, {postId:4,content:'React.js'}, ]; function commentsForPost(post,comments){ return comments.filter(function(comment){ return comment.postId === post.id; }) } console.log(commentsForPost(post,comments)) // 0: {postId: 4, content: "Angular4"}1: {postId: 4, content: "React.js"}length: 2__