JS中数组与对象的遍历方法实例小结

arr=['snow','bran','king','nightking'];

arr.forEach(function(ele,index){
console.log(index);
console.log(ele)
})

var newarr=arr.map(function(i){
  return "hello "+i
});
console.log(newarr)

var newarr=arr.filter(function(i){
  return i == "bran"
});
console.log(newarr)

var yy=arr.some(function(i){
  return i.length>4
});
console.log(yy)       //true

var xx=arr.every(function(i){
  return i.length>4
});
console.log(xx)       //false

arr.reduce(callback, initialValue)

[0,1,2,3,4].reduce(function(previousValue, currentValue, index, array){
 return previousValue + currentValue;
});

var total = [0, 1, 2, 3].reduce(function(a, b) {
  return a + b;
});
// total == 6
var flattened = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
  return a.concat(b);
});
// flattened is [0, 1, 2, 3, 4, 5]

var total = [0, 1, 2, 3].reduce(function(a, b) {
   return a + b;
},4);
console.log(total); //10

var obj={snow:1,bran:2,king:3,nightking:4};
for(let i in obj){
  console.log(i+','+obj[i])
}

for(let i in arr){
  console.log(i+','+arr[i])
}