遍历数组

for语句

var arr = [1,2,4,6]
for(var i = 0, len = arr.length; i < len; i++){
    console.log(arr[i])
}

foreach语句

var arr = [1,5,8,9]
arr.forEach(function(item) {
    console.log(item);
})

for-in语句

var obj = {
    name: 'test',
    color: 'red',
    day: 'sunday',
    number: 5
}
for (var key in obj) {
    console.log(obj[key])
}

for-of语句

var arr = [{name:'bb'},5,'test']
for (item of arr) {
    console.log(item)
}