map----映射--適合轉(zhuǎn)換
reduce---匯總--一個
filter---過濾--適合篩選
forEach---迭代（循環(huán)）
/*
map---映射---一個對一個
reduce---匯總---一堆出來一個（適合算總數(shù)和平均分）
filter---過濾器
forEach---循環(huán)（迭代）
*/
let arr5 = [1,2,3];
// let res = arr5.map(function(item){
// return item * 2;
// })
let res = arr5.map(item=>item*2);
let score = [12,2,38,88,99,44];
let results = score.map(item=>item>=60?'不及格':'及格');
console.log(results);
//reduce----算總和
/*let arr6 = [12,34,55,77,11];
let res6 = arr6.reduce(function(tmp,item,index){//tmp前兩個相加的結(jié)果，item數(shù)值,index索引
return tmp + item;
})
console.log(res6);*/
//reduce---算平均數(shù)
let arr7 = [12,34,55,77,11];
let res7 = arr7.reduce(function(tmp,item,index){
if(index != arr7.length -1){//不是最后一次
return tmp + item;
}else{
return (tmp+item)/arr7.length;
}
})
console.log(res7)
//filter---過濾
var arr8 = [12,345,56,678,9,19];
/*var res8 = arr8.filter(function(item){
if(item%3 == 0){//能被3整除的留下
return true;
}else{
return false;
}
})*/
var res8 = arr8.filter(item=>item%3 == 0)
console.log(res8);
let arr9 = [
{title:'男鞋',price:45},
{title:'女鞋',price:324345},
{title:'男報',price:445},
{title:'女包',price:2345},
]
let res9 = arr9.filter(json=>json.price>=1000);
console.log(res9);
//forEach
let arr10 = [12,34,56,7];
let res10 = arr10.forEach((item,index)=>{
console.log(index+':'+item)
});
