Javascript和for循环问题

Question

Is something wrong with my code? I was expecting my code:

years=new Array();
for (i = 0; i < 5; ++i) {
    for (j = 1; j < 13; ++j) {
        player.push(Math.round( nestedData[i].value[j] ))
    }

    years.push(player)
}

console.log(years)

to print something like:

    [array[12],array[12],array[12],array[12]]

but the result that i get is:

    [array[60],array[60],array[60],array[60]]

Answer 1

Create a new player array inside the first for loop. The problem with your code is that the values were being pushed into the same array instance.

var years = [];
for (i = 0; i < 5; ++i) {
    var player = [];
    for (j = 1; j < 13; ++j) {
        player.push(Math.round( nestedData[i].value[j] ))
    }
    years.push(player)
}

console.log(years)

Answer 2

As an addition to the correct answer already, please use var to declare your variables:

for (var i=0; i < 5; ++i) {
    var player = [];
    for (var j = 1; j < 13; ++j) {
        ...

Otherwise, it will use i as a global variable, which could end poorly if you have two functions looping at the same time, eg:

function loopone() {
   //wouldn't expect this to be an infinite loop eh?
   for (i=0; i < 100; i++) {
       looptwo();
   }
}
function looptwo() {
   for (i=0; i < 10; i++) {
   }
}