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# JavaScript Module Examples
Most of the examples in this section use the same input data:
```js
const myCars = [
{
car: 'Audi',
price: 40000,
color: 'blue',
},
{
car: 'BMW',
price: 35000,
color: 'black',
},
{
car: 'Porsche',
price: 60000,
color: 'green',
},
];
```
## Example `fields` option
```js
{
fields: [
// Supports pathname -> pathvalue
'simplepath', // equivalent to {value:'simplepath'}
'path.to.value' // also equivalent to {value:'path.to.value'}
// Supports label -> simple path
{
label: 'some label', // Optional, column will be labeled 'path.to.something' if not defined)
value: 'path.to.something', // data.path.to.something
default: 'NULL' // default if value is not found (Optional, overrides `defaultValue` for column)
},
// Supports label -> derived value
{
label: 'some label', // Optional, column will be labeled with the function name or empty if the function is anonymous
value: (row, field) => row[field.label].toLowerCase() ||field.default,
default: 'NULL' // default if value function returns null or undefined
},
// Supports label -> derived value
{
value: (row) => row.arrayField.join(',')
},
// Supports label -> derived value
{
value: (row) => `"${row.arrayField.join(',')}"`
},
]
}
```
## Default parsing
```js
const { Parser } = require('json2csv');
const json2csvParser = new Parser();
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"car","price","color"
"Audi",40000,"blue"
"BMW",35000,"black"
"Porsche",60000,"green"
```
## Specify fields to parse
```js
const { Parser } = require('json2csv');
const fields = ['car', 'color'];
const json2csvParser = new Parser({ fields });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"car","color"
"Audi","blue"
"BMW","black"
"Porsche","green"
```
## Use custom headers
```js
const { Parser } = require('json2csv');
const fields = [
{
label: 'Car Name',
value: 'car',
},
{
label: 'Price USD',
value: 'price',
},
];
const json2csvParser = new Parser({ fields });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"Car Name","Price USD"
"Audi",40000
"BMW",35000
"Porsche",60000
```
## Parse nested properties
You can specify nested properties using dot notation.
```js
const { Parser } = require('json2csv');
const myCars = [
{
car: { make: 'Audi', model: 'A3' },
price: 40000,
color: 'blue',
},
{
car: { make: 'BMW', model: 'F20' },
price: 35000,
color: 'black',
},
{
car: { make: 'Porsche', model: '9PA AF1' },
price: 60000,
color: 'green',
},
];
const fields = ['car.make', 'car.model', 'price', 'color'];
const json2csvParser = new Parser({ fields });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"car.make", "car.model", "price", "color"
"Audi", "A3", 40000, "blue"
"BMW", "F20", 35000, "black"
"Porsche", "9PA AF1", 60000, "green"
```
## Use a custom delimiter
For example, to create tsv files
```js
const { Parser } = require('json2csv');
const json2csvParser = new Parser({ delimiter: '\t' });
const tsv = json2csvParser.parse(myCars);
console.log(tsv);
```
will output to console
```
"car" "price" "color"
"Audi" 10000 "blue"
"BMW" 15000 "red"
"Mercedes" 20000 "yellow"
"Porsche" 30000 "green"
```
If no delimiter is specified, the default `,` is used.
## Use custom formatting
For example, you could use `*` as quotes and format numbers to always have 2 decimals and use `,` as separator.
To avoid conflict between the number separator and the CSV delimiter, we can use a custom delimiter again.
```js
const {
Parser,
formatters: { string: stringFormatter, number: numberFormatter },
} = require('json2csv');
const json2csvParser = new Parser({
delimiter: ';',
formatters: {
string: stringFormatter({ quote: '*' }),
number: numberFormatter({ separator: ',', decimals: 2 }),
},
});
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
*car*;*price*;*color*
*Audi*;40000,00;*blue*
*BMW*;35000,00;*black*
*Porsche*;60000,00;*green*
```
## Format the headers differently
For example, you can not quote the headers.
```js
const { Parser } = require('json2csv');
const json2csvParser = new Parser({
formatters: {
header: stringFormatter({ quote: '' },
},
});
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
car, price, color
"Audi",40000,"blue"
"BMW",35000,"black"
"Porsche",60000,"green"
```
## Unwind arrays
You can unwind arrays similar to MongoDB's \$unwind operation using the `unwind` transform.
```js
const {
Parser,
transforms: { unwind },
} = require('json2csv');
const myCars = [
{
carModel: 'Audi',
price: 0,
colors: ['blue', 'green', 'yellow'],
},
{
carModel: 'BMW',
price: 15000,
colors: ['red', 'blue'],
},
{
carModel: 'Mercedes',
price: 20000,
colors: 'yellow',
},
{
carModel: 'Porsche',
price: 30000,
colors: ['green', 'teal', 'aqua'],
},
];
const fields = ['carModel', 'price', 'colors'];
const transforms = [unwind({ paths: ['colors'] })];
const json2csvParser = new Parser({ fields, transforms });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"carModel","price","colors"
"Audi",0,"blue"
"Audi",0,"green"
"Audi",0,"yellow"
"BMW",15000,"red"
"BMW",15000,"blue"
"Mercedes",20000,"yellow"
"Porsche",30000,"green"
"Porsche",30000,"teal"
"Porsche",30000,"aqua"
```
## Unwind of nested arrays
You can also unwind arrays multiple times or with nested objects.
```js
const {
Parser,
transforms: { unwind },
} = require('json2csv');
const myCars = [
{
carModel: 'BMW',
price: 15000,
items: [
{
name: 'airbag',
color: 'white',
},
{
name: 'dashboard',
color: 'black',
},
],
},
{
carModel: 'Porsche',
price: 30000,
items: [
{
name: 'airbag',
items: [
{
position: 'left',
color: 'white',
},
{
position: 'right',
color: 'gray',
},
],
},
{
name: 'dashboard',
items: [
{
position: 'left',
color: 'gray',
},
{
position: 'right',
color: 'black',
},
],
},
],
},
];
const fields = [
'carModel',
'price',
'items.name',
'items.color',
'items.items.position',
'items.items.color',
];
const transforms = [unwind({ paths: ['items', 'items.items'] })];
const json2csvParser = new Parser({ fields, transforms });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"carModel","price","items.name","items.color","items.items.position","items.items.color"
"BMW",15000,"airbag","white",,
"BMW",15000,"dashboard","black",,
"Porsche",30000,"airbag",,"left","white"
"Porsche",30000,"airbag",,"right","gray"
"Porsche",30000,"dashboard",,"left","gray"
"Porsche",30000,"dashboard",,"right","black"
```
## Unwind array blanking the repeated fields
You can also unwind arrays blanking the repeated fields.
```js
const {
Parser,
transforms: { unwind },
} = require('json2csv');
const myCars = [
{
carModel: 'BMW',
price: 15000,
items: [
{
name: 'airbag',
color: 'white',
},
{
name: 'dashboard',
color: 'black',
},
],
},
{
carModel: 'Porsche',
price: 30000,
items: [
{
name: 'airbag',
items: [
{
position: 'left',
color: 'white',
},
{
position: 'right',
color: 'gray',
},
],
},
{
name: 'dashboard',
items: [
{
position: 'left',
color: 'gray',
},
{
position: 'right',
color: 'black',
},
],
},
],
},
];
const fields = [
'carModel',
'price',
'items.name',
'items.color',
'items.items.position',
'items.items.color',
];
const transforms = [
unwind({ paths: ['items', 'items.items'], blankOut: true }),
];
const json2csvParser = new Parser({ fields, transforms });
const csv = json2csvParser.parse(myCars);
console.log(csv);
```
will output to console
```
"carModel","price","items.name","items.color","items.items.position","items.items.color"
"BMW",15000,"airbag","white",,
,,"dashboard","black",,
"Porsche",30000,"airbag",,"left","white"
,,,,"right","gray"
,,"dashboard",,"left","gray"
,,,,"right","black"
```