Remove first element/array of an array in JavaScript

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'
},

What other code do you have? shift shouldn't give you this error I think. — putvande
– putvande, Commented Sep 21, 2017 at 10:31
Where is your myArray? I see your snippets and you don't have myArray in any of it. If based on what you are showing you did a myArray.data then you are trying to shift() on an Object. — Matt
– Matt, Commented Sep 21, 2017 at 12:14

marvel308 · Accepted Answer · 2017-09-21 10:32:17Z

3

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]);

answered Sep 21, 2017 at 10:32

marvel308

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1 Comment

Samurai Jack Over a year ago

In my case it doesn't work... I added another snippet of code. Maybe now it is more clear

Pawan sasanka · Accepted Answer · 2017-09-21 10:55:28Z

1

.shift() is working fine.

Problem is in your Array which is going to shift, Check whether myArray.data consists of data, Error says you are trying to shift a value from a undefined (null) object.

splice(0,1) also working fine

answered Sep 21, 2017 at 10:55

Pawan sasanka

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Comments

Alexander Elgin · Accepted Answer · 2017-09-21 10:46:03Z

0

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

edited Sep 21, 2017 at 10:46

answered Sep 21, 2017 at 10:30

Alexander Elgin

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