Convert array of objects to array of arrays of strings

Question

Suppose I have the following structure:

var obj = [{one: 1, two: 2, three: 3}, {one: 1, two: 2, three: 3}];

But I need to export this data to csv with the following output:

"1", "2", "3"
"1", "2", "3"

I've tried the following code, but it does not work:

var csvContent = "data:text/csv;charset=utf-8,";

Object.values = function (obj) {
    var vals = [];
    for( var key in obj ) {
        if ( obj.hasOwnProperty(key) ) {
            vals.push(obj[key]);
        }
    }
    return vals;
}

Object.values(obj).forEach(function(infoArray, index) {
    dataString = infoArray.join(",");
    csvContent += index < obj.length ? dataString + "\n" : dataString;
});

var encodedUri = encodeURI(prepearedString);
var link = document.createElement("a");
link.setAttribute("href", encodedUri);
link.setAttribute("download", "my_data.csv");
document.body.appendChild(link);
link.click();
document.body.removeChild(link);

Could you please help me with this issue.

encodeURI(prepearedString)? Maybe encodeURI(csvContent) works better? — Malk
– Malk, Commented Jun 22, 2015 at 20:39
Please elaborate. What do you mean by "does not work"? People are usually happy to provide a solution, but usually do not find joy in having to figure out what the problem is first. — Aaron Cicali
– Aaron Cicali, Commented Jun 22, 2015 at 20:42

Blixt · Accepted Answer · 2015-06-22 20:40:49Z

It looks as if you're converting objects to a CSV file. It's important to note that objects are basically hash maps which means that the keys are not accessed in a predictable order. Also, some of your rows may be missing a value, which would cause holes in your resulting data.

What I would do is to first transform all the rows into columns (and default to null wherever a value is missing) so that you can predictably access the values for all known columns. Then you can output a CSV header with all known headers, followed by the values.

Here's an example:

var rows = [{one: 1, two: 2, three: 3}, {one: 1, two: 2, three: 3}];

var columns = {};
rows.forEach(function (row, index) {
    for (var key in row) {
        if (!columns[key]) {
            // Set up nullified column.
            var values = [];
            for (var i = 0; i < rows.length; i++) {
                values.push(null);
            }
            columns[key] = values;
        }
        // Store the value in the column.
        columns[key][index] = row[key];
    }
});

// Print the header.
var header = Object.keys(columns);
console.log(header.join(','));
// Print the rows.
for (var i = 0; i < rows.length; i++) {
    var values = header.map(function (key) { return columns[key][i]; });
    console.log(values.join(','));
}

This is the output you get in the console from the above code:

one,two,three
1,2,3
1,2,3

vinayakj · Accepted Answer · 2015-06-22 20:46:26Z

1

Below is the code to extract values and have multilined them, CSV format can be managed.

var obj = [{one: 1, two: 2, three: 3}, {one: 1, two: 2, three: 3}];
var output = [];

for( var key in obj ) {
            for( var k in obj[key]){
                   output.push(obj[key][k])
                  }
        output.push('\n')
}
alert(output.join(''))

answered Jun 22, 2015 at 20:46

vinayakj

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2 Comments

Blixt Over a year ago

A few notes: 1) for ... in on an array isn't really safe – use forEach or iterate indexes 0..length and 2) for ... in doesn't have to run in a predictable order since objects are hashmaps, and shouldn't be relied upon, especially if the objects in the array are even slightly different.

vinayakj Over a year ago

agree.. should be used for loop, as for in loop also considers enumerable properties, but specific to this obj, seems no additional properties so used it.

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