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Introduction to the filter() array filtering method in es6 (with code)

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Release: 2019-03-20 10:32:29
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This article brings you an introduction to the filter() array filtering method in es6 (with code). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. Create an array and determine whether a certain value exists in the array

var newarr = [
  { num: 1, val: 'ceshi', flag: 'aa' },
  { num: 2, val: 'ceshi2', flag: 'aa2'  }
]
console.log(newarr.filter(item => item.num===2 ))
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2. You can also use the above method to filter out those with num of 2 and leave those with num of 1

var newarr = [
  { num: 1, val: 'ceshi', flag: 'aa' },
  { num: 2, val: 'ceshi2', flag: 'aa2'  }
]
console.log(newarr.filter(item => item.num!=2 ))
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3. Remove empty strings, undefined, and null from empty arrays

var arr = ['1','2',undefined, '3.jpg',undefined]
var newArr = arr.filter(item => item)
console.log(newArr)
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var arr = ['1','2',null, '3.jpg',null]
var newArr = arr.filter(item => item)
console.log(newArr)
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//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)
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4. Remove non-conforming items from the array

var arr = [20,30,50, 96,50]
var newArr = arr.filter(item => item>40)  
console.log(newArr)
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5. Filter non-conforming items

var arr = ['10','12','23','44','42']
var newArr = arr.filter(item => item.indexOf(&#39;2&#39;)<0) 
console.log(newArr)
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6. Array deduplication

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]
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