在JavaScript中删除数组的第一个元素/数组

Question

I have a problem with removing the first element of an array.

To be short, this is how my array looks like if I show it in console:

(11) [Array(4), Array(4), Array(4), Array(4), Array(4), Array(4), Array(4), Array(4), Array(4), Array(4), Array(4)]
0 : (4) ["2017-09-20T16:00:00-07:00", 188.125, 0, 1]
1 : (4) ["2017-09-20T17:00:00-07:00", 123.125, 0, 1]
2 : (4) ["2017-09-20T18:00:00-07:00", 114.25, 0, 1]
3 : (4) ["2017-09-20T19:00:00-07:00", 115, 0, 1]
4 : (4) ["2017-09-20T20:00:00-07:00", 113.25, 0, 1]
5 : (4) ["2017-09-20T21:00:00-07:00", 115.625, 0, 1]
6 : (4) ["2017-09-20T22:00:00-07:00", 114.75, 0, 1]
7 : (4) ["2017-09-20T23:00:00-07:00", 114, 0, 1]
8 : (4) ["2017-09-21T00:00:00-07:00", 112.625, 0, 1]
9 : (4) ["2017-09-21T01:00:00-07:00", 108.375, 0, 1]
10 : (4) ["2017-09-21T02:00:00-07:00", 111.125, 0, 1]
length : 11
__proto__ : Array(0)

I want to remove the first one, 0 , I tried using .shift() but didn't work.

Like my array is called myArray.data and I tried myArray.data.shift() and I get this error message:

TypeError: Cannot read property '0' of undefined
    at bundle.js:1554
    at Function._.map._.collect (vendor.js:11761)
    at renderChart (bundle.js:1547)
    at bundle.js:1611
    at Scope.$digest (vendor.js:34716)
    at Scope.$apply (vendor.js:34986)
    at bundle.js:259
    at vendor.js:14387
    at _fulfilled (vendor.js:13992)
    at self.promiseDispatch.done (vendor.js:14021)

Any ideas how to solve this?

Later edit:

The code is inside a chart generation function, this is the whole snippet:

data: {
    type: chartType,
    columns: [
        ['x'].concat(_.map(myArray.data, function (dataPoint) {

        const x = (myArray.data).shift();
        console.log(myArray.data);          
        console.log(x);

            return moment(dataPoint[0]).valueOf();
        })),
        ['Expected'].concat(_.map(myArray.data, function (dataPoint) {
            return dataPoint[1];
        })),
        ['Actual'].concat(_.map(myArray.data, function (dataPoint) {
            return dataPoint[1];
        }))
    ],
    x: 'x'
},

Answer 1

I can reproduce the result wanted using Array.shift()

 let arr = [ ["2017-09-20T16:00:00-07:00", 188.125, 0, 1], ["2017-09-20T17:00:00-07:00", 123.125, 0, 1], ["2017-09-20T18:00:00-07:00", 114.25, 0, 1], ["2017-09-20T19:00:00-07:00", 115, 0, 1], ["2017-09-20T20:00:00-07:00", 113.25, 0, 1], ["2017-09-20T21:00:00-07:00", 115.625, 0, 1], ["2017-09-20T22:00:00-07:00", 114.75, 0, 1], ["2017-09-20T23:00:00-07:00", 114, 0, 1], ["2017-09-21T00:00:00-07:00", 112.625, 0, 1], ["2017-09-21T01:00:00-07:00", 108.375, 0, 1], ["2017-09-21T02:00:00-07:00", 111.125, 0, 1] ]; console.log(arr[0]); arr.shift(); console.log(arr[0]); 

Answer 2

You can remove the first array item usingz myArray.data.splice(0, 1) but the error tells that you are trying to apply array method to undefined value. Perhaps the $scope has not received the value yet

Answer 3

.shift() is working fine. 

问题出在要移动的Array中，请检查myArray.data是否包含数据，Error表示您正在尝试从未定义（空）对象中移动值。

splice(0,1) also working fine