untranspose

Convert column-oriented arrays into row-oriented objects.

untranspose is a small CommonJS utility for turning data shaped like this:

{
  name: ["Ada", "Grace"],
  language: ["Lovelace", "COBOL"]
}

into data shaped like this:

[
  { name: "Ada", language: "Lovelace" },
  { name: "Grace", language: "COBOL" }
]

Installation

npm install untranspose

Usage

const untranspose = require("untranspose");

const rows = untranspose({
  id: [1, 2, 3],
  name: ["Ada", "Grace", "Katherine"],
  active: [true, false, true]
});

console.log(rows);
// [
//   { id: 1, name: "Ada", active: true },
//   { id: 2, name: "Grace", active: false },
//   { id: 3, name: "Katherine", active: true }
// ]

API

untranspose(data, emptyValue)

Returns an array of row objects.

data

Type: Object

An object whose keys are field names and whose values are arrays.

untranspose({
  a: ["a1", "a2"],
  b: ["b1", "b2"]
});
// [
//   { a: "a1", b: "b1" },
//   { a: "a2", b: "b2" }
// ]

The number of output rows is based on the length of the first field's array.

untranspose({
  a: [1, 2, 3],
  b: ["one"]
});
// [
//   { a: 1, b: "one" },
//   { a: 2 },
//   { a: 3 }
// ]

If data has no fields, the result is an empty array.

untranspose({});
// []

emptyValue

Type: any

Default: undefined

Values that are strictly equal to emptyValue are omitted from each row. By default, undefined values are omitted.

untranspose({
  name: ["Ada", "Grace"],
  score: [100, undefined]
});
// [
//   { name: "Ada", score: 100 },
//   { name: "Grace" }
// ]

You can pass a custom value to omit:

untranspose({
  name: ["Ada", "Grace"],
  score: [100, null]
}, null);
// [
//   { name: "Ada", score: 100 },
//   { name: "Grace" }
// ]

Falsy values are preserved unless they match emptyValue.

untranspose({
  count: [0, 1],
  enabled: [false, true],
  label: ["", "ready"]
});
// [
//   { count: 0, enabled: false, label: "" },
//   { count: 1, enabled: true, label: "ready" }
// ]

CommonJS

This package uses CommonJS:

const untranspose = require("untranspose");

TypeScript

Type definitions are included.

import untranspose = require("untranspose");

const rows = untranspose({
  id: [1, 2, 3],
  name: ["Ada", "Grace", "Katherine"],
  score: [100, undefined, 95]
});

// rows is Array<{
//   id?: number;
//   name?: string;
//   score?: number;
// }>

With esModuleInterop or compatible module settings, default imports can also work in TypeScript projects:

import untranspose from "untranspose";

Development

Run the test suite with:

npm test

License

MIT