1.数组去除空值
function filter_array(array) {
return array.filter(item=>item);
}
//JS
var t = [false, null, 0, NaN, undefined, "",'aaaa'];
t.filter(function (item) { return item });
t.filter(function (item) { return item.IsCurrent == true;}
2.通过某元素获取在数组中对应的下标（也是判断是否存在于这个数组中）
//ES6
var t = [{id:1},{id:2},{id:3}];
var tt = {id:3};
t.map(item => item.id ).indexOf(tt.id)
//JS
var t = [{id:1},{id:2},{id:3}];
var tt = {id:3};
t.map(function (item) { return item.id}).indexOf(tt.id)
3.改变数组对象中元素的值
//JS
var t = [{id:1},{id:2},{id:3}];
t.map(function (item) { return item.id = 55})
4.数组去重
let arr = [1,2,3,4,4,1]
let newArr = arr.reduce((pre,cur)=>{
if(!pre.includes(cur)){
return pre.concat(cur)
}else{
return pre
}
},[])
console.log(newArr);// [1, 2, 3, 4]
5.计算数组中每个元素出现的次数
let names = ['Alice', 'Bob', 'Tiff', 'Bruce', 'Alice'];
let nameNum = names.reduce((pre,cur)=>{
if(cur in pre){
pre[cur]++
}else{
pre[cur] = 1
}
return pre
},{})
console.log(nameNum); //{Alice: 2, Bob: 1, Tiff: 1, Bruce: 1}
6.对象里的属性求和
var result = [
{
subject: 'math',
score: 10
},
{
subject: 'chinese',
score: 20
},
{
subject: 'english',
score: 30
}
];
var sum = result.reduce(function(prev, cur) {
return cur.score + prev;
}, 0);
console.log(sum) //60
