数组去重.

1.

var arr=[1,2,3,3,2,'hello','hello'];
function unique(arr){
    for(let i=0;i<arr.length;i++){
        for(let j=i+1;j<arr.length;j++){
            if(arr[i]==arr[j]){
                arr.splice(j,1);
                j--;
            }
        }
    }
}
unique(arr);
console.log(arr);

2.indexOf()

3.

lastIndexOf()
var arr=[1,2,3,3,2,'hello','hello'];
function unique(arr){
    let newArr=[];
    for(let i=0;i<arr.length;i++){
        if(newArr.lastIndexOf(arr[i])===-1){
            newArr.push(arr[i])
        }
    }
return newArr;
}
console.log(unique(arr));

4.includes

var arr=[1,2,3,4];
console.log(arr.includes(6));
var arr=[1,2,3,3,2,'hello','hello'];
function unique(arr){
    let newArr=[];
    for(let i=0;i<arr.length;i++){
        if(!newArr.includes(arr[i])){
            newArr.push(arr[i]);
        }
    }
return newArr;
}
console.log(arr[i]);

5.forEach+indexof

var arr=[1,2,3,3,2,'hello','hello'];
function unique(arr){
    let newArr=[];
    arr.forEach(function(item){
        if(newArr.indexOf(item)===-1){
            newArr.push(item);
        }
    })
return newArr;
}
console.log(unique(arr));

6.filter+indexOf/includes

var arr=[1,2,3,3,2,'hello','hello'];
function unique(arr){
	let newArr=[];
	return arr.filter(function(item){
		return newArr.includes(item)?"":newArr.push(item)
	})
	return newArr;
}
console.log(unique(arr));

7.set去重

var arr=[1,2,3,3,2,'hello','hello'];
let set=new Set(arr);
console.log(set);
console.log(Array.from(set));
console.log([...set]);
map 
var arr=[
	{
		id:1,
		name:"zhangsan"
	},{
		id:2,
		name:"lisi"
	},{
		id:3,
		name:"wangwu"
	}
];
var res=arr.map(function(item){
	return item.name
});
console.log(res);