filter() 数组过滤方法总结

1.创建一个数组，判断数组中是否存在某个值

var arr = [
  { name:'xdd',  age:50},
  { name: 'xm', age: 12  }
]
var newArr = arr.filter(item => item.name=='xdd' )
// newArr :  [{name:'xdd',  age:50}]

2.去除 ‘’ ,undefined,null, 0

var arr = ['1',2,undefined, 'xdd',undefined,'0', 0, null, []]
var newArr = arr.filter(item => item)
// newArr : ['1','2','xdd', '0', []]

3.去掉数组中不符合项

var arr = [1, 2, 3, 4, 5,4, 6]
var newArr = arr.filter(item => item>4) 
// newArr : [5, 6]

4.数组去重

var arr = [1, 2, 6, 3, 4, 5,4, 6,4,5,6,1,5,5,6,2]
var newArr = 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 self.indexOf(x)===index
})
// newArr: [1,2,6,3,4,5]