Loop nested array and return values by index

Question

I have a nested array that holds a handful of coordinates. I am trying to loop the nested array and log the values of each coordinate.

I can get it working in Python, but I need it in JavaScript. Here is how it works in python:

list_of_coordinates = [(100, 98), (200, 78)]
for i in list_of_coordinates:
    x_coord = i[0]
    y_coord = i[1]
    print(x_coord, y_coord)

The output of the above is:

100 98
200 78

When I try to do this in Javascript I get the output of 0 and 1... not the actual coordinate values.

let listOfCoordinates = [[100, 0], [200, 1]];
for (const i in listOfCoordinates) {
    let xCoord = i[0];
    let yCoord = i[1];
    console.log(xCoord, yCoord);
}

The output of this is

0 undefined
1 undefined

listOrCoordinates.forEach(coord => console.log(coord[0], coord[1])); would also do the same thing — Taplar
– Taplar, Commented Jul 31, 2020 at 17:29

norbitrial · Accepted Answer · 2020-07-31 17:28:59Z

3

You should use for..of instead as the following:

let listOfCoordinates = [[100, 0], [200, 1]];
for (const i of listOfCoordinates) {
    let xCoord = i[0];
    let yCoord = i[1];
    console.log(xCoord, yCoord);
}

See from the documentation:

The for...of statement creates a loop iterating over iterable objects, including: built-in String, Array, array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined iterables. It invokes a custom iteration hook with statements to be executed for the value of each distinct property of the object.

edited Jul 31, 2020 at 17:28

answered Jul 31, 2020 at 17:27

norbitrial

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1 Comment

ubuntuuber Over a year ago

haha. Amazing. I've spent the past 30mins googling this. Thank you!

Taplar · Accepted Answer · 2020-07-31 17:32:00Z

0

forEach way, with deconstruction of the input.

let listOfCoordinates = [[100, 0], [200, 1]];

listOfCoordinates.forEach(([xCoord, yCoord]) => console.log(xCoord, yCoord));

answered Jul 31, 2020 at 17:32

Taplar

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Comments

ADJenks · Accepted Answer · 2020-07-31 17:35:10Z

0

Correct way, if you want to continue to use for...in:

const listOfCoordinates = [[100, 0], [200, 1]];
for (let i in listOfCoordinates) {
    let xCoord = listOfCoordinates[i][0];
    let yCoord = listOfCoordinates[i][1];
    console.log(xCoord, yCoord);
}

Because you named the variable "i", which is often short for "index", I thought you'd want it to be an index, which would use the "in" form.

The for...of form returns the values. It could be written like so:

const listOfCoordinates = [[100, 0], [200, 1]];
    for (let coord of listOfCoordinates) {
        let xCoord = coord[0];
        let yCoord = coord[1];
        console.log(xCoord, yCoord);
    }

edited Jul 31, 2020 at 17:35

answered Jul 31, 2020 at 17:30

ADJenks

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Comments

Nina Scholz · Accepted Answer · 2020-07-31 17:41:00Z

0

You could take for ... of statement and a destructuring assignment to the wanted variables.

let listOfCoordinates = [[100, 0], [200, 1]];

for (const [xCoord, yCoord] of listOfCoordinates) {
    console.log(xCoord, yCoord);
}

answered Jul 31, 2020 at 17:41

Nina Scholz

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